GLOC does the Red Sea on MV Tala

MV Tala is a dive boat with a difference, whilst she isn't at the top end of the luxury liveaboard market and that might put some people off, she is at the top when it comes to technical diving in the DIR style. She has a competent skilled crew (topside and dive guides) who let you get on with what you want to do - dive. Mixed gas diving is catered for effortlessly with discounts being applied to standard DIR mixes, doubles and stages are the rule rather than the exception, and they can cater for any diving from simple singles reef dives to multiple stages dives to depths in excess of 100m.

The trip that I have just come back from was organised through DIRx and involved 9 people from all over the UK and one diver from Belgium meeting up in Hurghada on the 9th November. Lots of unpacking and fettling ensued before we started an excellent week's diving. Diving started with a wakeup call at 05:45 and in the water for 06:30-07:00, the first of 4 dives per day. Wrecks that were covered included the Giannis-D, Carnatic, Marcus, Kimon-M, Rosalie Muller, Salem Express, Ulysses, El Mina and the Poseidonia, and reefs that were dived were too numerous to mention. In 6 days I manged 20 dives after missing out on 2 night dives as they were getting a little samey (being a wreck diver rather than a fish diver). A full trip report was written by Iain Smith and can be found here.

Here are some pictures from the trip and more can be seen on my website here

Cave 1 for the Chimps

January 2008 will see 3 of the Chimps jetting off to Mexico to conduct some further training with Chris Le Maillot, Fred Devos and Danny Riordan at DIR-Mexico. Unfortunately due to a clash in dates Howard will finish his course just as GLOC and Garf arrive!! Garf and GLOC are watching with interest as to whether Howard can organise his way out there without the help of the team admin bitch - GLOC!!

Unfortunately due to monetary and time pressures, we have decided that 2008 is not the year to do Tech 2 as it would be much better to gain the additional skillset from Cave 1 and consolidate the Tech 1 skills that we have learned. It will also allow us to go to France and not get blown out in the caves there if the Summer of 2008 is anything like 2007!

Commitment to Training

GLOC is in hog heaven. He is having to organise gas, logistics, accommodation, an instructor, flights, etc, etc, oh my. Howard is in negotiations for a bulk purchase of bananas. I am digging around at the bottom of my dive kit box looking for my control freak Hat. Training will commence over the winter, and then the chimps will attempt GUE Tech 2 next summer / Autumn. OOK OOK

The DIR Head to Toe Check

The DIR Head to Toe Check

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The DIR Head to toe check is something that gets taught to you and drilled in to you in every training course. At the fundies level, it can seem overkill, as it takes a couple of minutes, and some of the items checked just seem ridiculous. At the Tech1 level and above, the reasons for the checks become more obvious, and indeed can be suitably demonstrated by the instructor failing the piece of kit if he/she sees you missing a piece of the check. You have already checked a great deal of this when actually putting the kit on, but this is a check witnessed by the whole team, when you are about to hit or go under the water. the purpose of the check is to ensure that everything required to get you and the team back out of the water safely is attached properly, and working properly, so that you don't find out when you need it that it is not there. Lots of divers do a predive check, but many people do many different versions of it. If you are diving with someone new, how do you know what they will check etc. We do this the same way within our team every time, because the time you don't is the time you miss something.

Anyway, someone asked me to document it for them, so I just thought it might make an interesting excercise to write and expand it into an article. . The check, as the name suggests, begins at the head and ends at the toes. The precise order seems to vary depending on who is doing it, but the principle of moving down the body is sound, as it prompts you to remember things you may otherwise have forgotten. The check is done either on the boat in the sea, or in the water inland. It's worth noting at this point, that this head to toe forms part of the GUE EDGE pre dive checks (winner of the dumbest name in world history award). Anyway, on we go.

The check is done as a team. Each person is checking their own kit, but looking to the others to confirm they have actually checked theirs, and in some cases, doing the check for them. Each team member will have a role assigned to them for the dive. This will dictate their position in the water - diver 1 will lead, and in a three man team diver 3 will bring up the rear. This team element also manifests itself during kitting up, and during the head to toe check. Although each person will check their own kit, Diver 1 will check diver 2 where necessary, diver 2 will check diver 3 and diver 3 will check diver 1. This way everyone understands from the start who they will be checking, and nobody gets missed. It's all about making the checks flow smoothly. It is the same ethos that we use when doing a gas switch. 1 switches first, then 2 then 3.

Hood
Is it on. An obvious one, but I'm sure I'm not the only diver to have seen people jump in without a hood and practically leap back out of the water onto the boat to get it.

Mask
Is it on, and ready (demisted). Also, check your team's masks - are they trapping the hood and likely to flood once you descend. 20M per minute is not the time to find out your mask is flooding as it just becomes a stress factor and ups the breathing rate, and yet we see it all the time - divers having to stop on the ascent to sort things out. Whilst this might not be a big deal to them, we have a constant descent rate because we do not include the descent as part of bottom time for deco calculations - so stopping to sort something out for two minutes at 35 metres can bugger things up.

Valves - Flow Check
Reach behind you and check that all your valves are in the appropriate position - fully open for us. I've been guilty of leaving the isolator closed in the dark and hopefully distant past, descending with 200 bar, and surfacing with 200 bar. Oops. If you have deco bottles or stages, check that the valves are are again in the appropriate position - for us this means charged and then switched off. finally, check the suit inflation bottle if you have one. Again 20M per minute down to 50M becomes a real pain the arse if your argon bottle is switched off. We also perform another flow check at the bottom of a shotline in case anyone has rolled off a post against the line on the way down.

Regulators
Breathe Both regaulators in the water, so dip your head, breathe from the primary, do a switch to the necklaced reg and check it breathes. If your 2nd stages diaphram has become unseated, the reg will breathe lovely on the surface, and breathe water underwater. Not nice. Best to find out now than when you have to dinate gas to someone and find you have nothing left to breathe off.

Torch
Is your primary torch now deployed and in your head. Is it switched on and working. Are your backup torches in position. If not, get out of the water and sort it out. Trust me on this one

Modified S Drill
Take the second stage out of your mouth and hold it in your hand. Dip your head and undo the long hose. Undo it from the canister light and check it is free all the way back to the first stage. Hold it up in the air so your team mates can see it - they are the interested ones because they are the ones You are checking to make sure you can donate gas freely at any point, a critical piece of the configuration, yet it does get missed. We missed this once on Tech1 and spent a portion of the dive having to do mask to mask gas donations because the hoses were becoming trapped. Restow the hose carefully when you have finished. I was coaching a diver a few weeks ago and saw the same thing when he was kitting up and the inevitable out of gas I threw at him went predictably pie-shaped. I suspect he won't do it again.

Bubble check.
Whilst we're looking at the valves, let's check them for bubbles. Turn around onto your back and let your teammates look at your valves / manifold. Then let them check your suit inflation bottle and hoses, inflation valves, SPGs, deco bottles, stages. Diver 1 checks diver 2, diver 2 checks diver 3, diver 3 checks diver 1. This is a theme that goes all the way through DIR, each person has a role, and each person knows who they should be keeping an eye on / checking, so it happens smoothly and in an understood order. This takes practice.

Suit Dump Valve
Is it in the appropriate position. I forgot this on one of my fundies dives, leaving it mostly closed with air in the suit. It was a very uncomfortable dive, and the ascent was ludicrously messy as I now had a large bubble of gas to manage on the way up. Most divers I know just open it and leave it there, but the important thing is that you check it and it is in the position you want it to be in.

Suit Inflate Valve
Is the hose connected properly, can it be pulled off. Does it iactually inflate the suit properly without water ingressing. Suit squeeze - not nice

Wing Inflate
Is the hose connected properly or entangled. Can the low pressure hose be pulled off. Does the wing inflate.

Wing Dumps
Does the corrugated hose dump work effectively. Does the kidney dump work effectively. I missed this one on a Tech1 dive and found to my horror on the ascent that the string was not there. Kerslake denied cutting it, but who knows. You are checking to make sure you can actually reach it - you haven't got anything in the way, and that it functions correctly

Instruments
Have you remembered to put on the instruments on your arms? hold your arms up and let your team see - they might be counting on you to call the deco. GLOC's deco is shaky at the best of times, but when we arrived at 52 metres on the moldavia with nothing on his arms and showed us...well, you can imagine how the conversation went on the boat. An easy one to forget.

Weight system
How many times have you seen people jump in without weights. Easy at the start of the dive, especially in a twinset, but I bet its a sickening feeling realising as that twinset gets lighter when you realise that "something" that you were sure you had forgotten is what would have kept you from hitting the surface early.

Knife
Can you reach it, with both hands. Is it on the appropriate place on yoru harness so that your team mates know where to get it if they need it.

Pockets
We tell each other at this point what we are carrying in our pockets. This is pretty easy for us, as we are all carrying the same things, in the same pockets, but this is when someone goes "bugger, I forgot my SMB" when they tap their pockets to make sure they are appropriately full. This is also the time for people to deal with anything poking out of pockets for a team mate and tidy it away.

Deco Bottles
If you have clipped off your deco bottles to your hip d ring, have a team mate check to make sure that your main SPG coming off your left post is not clipped off THROUGH one of the hoses, making deployment of the deco regulator a job of either hvaing to thred it through, or removing the spg and then reattaching it. This was my biggest one on Tech1, kept doing this, and its amazing how much stress it adds when you can't pull the hose free. Whilst we are looking at each other's deco bottles, are the second stages stowed neatly away on all the bottles, and can we read the MOd markings clearly on the bottle for when we authorise a gas switch later in the dive.

Fins
Are we wearing them today GLOC?

The Chimps Do Scapa - Part 7

Dive 11. The James Barrie. 43 Metres. Bottom Gas 20/20. Decompression Gases 50% and 100%
Dive 12. The Brummer. 36 Metres. Bottom Gas 32%. Decompression Gas 100%

The morning got off to a ropy start when we ran out of coffee. David immediately experienced a fit from too low a partial pressure of caffeine in his blood system. Luckily, we were able to nab some from another location. Once everyone had calmed down, Gareth and Wilbo sat down to assist David with his planning. This was proving something of a consternation, as David's flavour of dive planning consists of "Point me in the general direction and push me off the wreck, we'll talk about the deco later". Once all the planning was done, Diane announced that she had finally figured out what Garf stands for. This intrigued me as I wasn't aware that it stood for anything. Apparently it stands for Grumpy and Really Fucked-off.

On to the dive. We kitted up and jumped in. I was diving with Howard and Wilbo but ascending alone, as we had struggled to obtain enough Helium and Oxygen the night before, so were all diving unique bizarre-o-mixes. To my delight, I could see the wreck at 20 metres, meaning there was at least 15 metres of vertical viz. Once on the wreck, I was amazed to see that the viz was limited by the ambient light, rather than particulate in the water.

The James Barrie was a 666 Icelandic Steam Trawler that foundered in Hoxa sound in 1969 following running aground in the Pentland Firth on her way to Hull. She now lies on her side in 43 metres of water, and makes for a stunning wreck as the water flooding into Scapa Flow flushes the area clear of silt. It also seems to stop some of the marine life from forming on the wreck, so the remains are remarkably well preserved.

If the Tabarka was the most atmospheric dive of the week, the James Barrie was the most fun. It's only a small wreck, and with 12 divers on it, including a photographer and three scooters, it was just a riot. Top moment was Howard Payne, doing a barrel roll, and messing it up, ending up on his back pinned to the seabed, with half a dozen divers laughing their heads off at him in the stunning viz. Scootering through the holds was amazing, as thy are well open, and, a first for me, the wreck was well lit with ambient light. I managed to get myself tied up in monofilament, but the guys told me to stop and unwrapped me with no dramas. It was just stunning, and everyone had a great time. All too soon, the time came to leave the wreck. Because I was on weird-o-mix, I had decided to take two deco bottles with me, so I ascended next to Gareth, Howard and Wilbo, so that they could watch me through the gas switches at 21 metres and 6 metres. This all went through with no issues, and the lads started playing around at 6 metres to relieve the boredom.

During the Surface Interval, the skipper tied up at Lyness, the Naval base for both WW1 and WW2. Being a military history buff, I always find this place amazing, incredibly atmospheric. The place is eerily quiet and deserted, but you can still hear echoes of the life the large base had during two world wars. Abandoned and rotting military gear lies around all over the place, and there is a small museum to be explored. At the museum is an interesting exhibition on the Royal Oak, a complex and interesting story in its own right, but enough in this context to say it brought the realities of Scapa Flow back to me.

After a couple of hours of SI and a hearty breakfast, we roped off to head back into the flow to dive the Brummer. Howard and Wilbo had decided to bin the final dive, as they had had enough, and wanted to get warmed up and packed. This left Gareth and I to do the final dive. The first moment of drama happened when Diane jumped in first, and experienced a massive suit flood. She waved frantically, and the boat came about for us to haul her out of the water. The second bit of drama happened when Gareth's twin set leaped off the shelving, shearing off the right post cleanly. Ooops. Luckily, it was just a two minute job to get Gareth out of his own kit, and into Wilbo's. And so off we jumped into the water to dive the Brummer. This is another small cruiser, and I remember it being fairly broken up. It appears that it has degraded even further in the last year. Although there are still many fantastic swim throughs, much of the plating is finely balanced on girders that look really shaky. We were lining into the wreck, and I decided that this was not the wreck to push too far, so we turned it and had a gentle 40 minute bimble, in and out of the wreck. There are still some stunning sights, with 5.9 inch guns a plenty, huge ventilator grills and winches on display. The wreck is covered in life, and is a really peaceful dive. All too soon it was time to leave the wreck. We were carrying Oxygen, so a relatively fast ascent was done up to 6 metres for the gas switch, and time to contemplate the week's diving.

Back on the boat, most people had begun packing away their kit, so Gareth and I dekitted and packed away our stuff as well. Once we had packed up the containers, we headed down the flattie bar for a few jars, and then off to the Royal Hotel for a meal. The group presented me with a brass replica of a sign for the officer's mess on the Markgraf, which came as a complete and very pleasant surprise, and then we all called it a night.

The Chimps Do Scapa - Part 6

Dive 9. SMS Markgraf. 42 Metres. 45 Minutes Bottom Time. 30 Minutes Decompression Time. 21/35 and 50%
Dive 10. SMS Karlsruhe. 25 Metres. 40 Minutes Bottom Time. 8 Minutes Decompression Time. 32% and Oxygen

The visibility on the Markgraf had dropped to about 5 metres, so we took the descent carefully. Gareth led the dive, and located the hole we were after almost immediately. However, Howard felt uncomfortable with the dive and called it immediately. As it was just a min deco ascent, we let him ascend on his own, and Gareth and I, as we felt ok, decided to continue with the dive. I tied off primary and secondary ties on the outside of the hole, and we made our way into the wreck. We past the point we had gone to the other day, and turned right deeper into the wreck. It opened up into a fairly large compartment, with several entrances, so we continued tying off and made our way out of the initial entrance and deeper into the wreck. We were now swimming parrallel to the keel of the wreck, and perhaps to decks in. Passing a hatch, we emerged into a corridor which went on for perhaps ten metres before coming to an area covered in cables and broken steel. It had taken us about ten minutes to reach this point, and although we were well within the rule of thirds we had set out when making the primary tie-off, I decided enough was enough and I turned the dive. Gareth collected the tie offs for me as he swam ahead and I reeled back. We exited the wreck three minutes later and stowed away the reel with no dramas. I felt at this point the wreck no longer held any fear for me, and I had really enjoyed penetrating it, seeing areas I had not seen before. It also gave me a healthy respect for the escape we made last year - turning the wrong way would obviously had been fatal.

Outside the wreck, we swam the small distance to the bows, at which point Gareth indicated he wanted to take a couple of shots with his camera. I did the posing thing over the bows whilst he took the pictures, but these did not come out well. We decided to do a swimming ascent, so swim very slowly up the keel of the wreck, which took us from 43 metres all the way to 24 metres, giving you a real image of the scale of these battleships. At 24 metres, we called the dive, and ascended just three metres above the wreck to switch gas to 50% and shoot the bag. Talk about an easy ascent. The deco was uneventful, and back on the surface, we could see Howard on the Invincible keeping an eye out for us, so all was well. Everyone seemed to enjoy their dive, although Mary had one surreal moment when, whilst swimming INSIDE the Markgraf, she came across a green Morphy Richards Hoover. Complete with plug. Despite the jokes about deep air that were made all day she insists it was there, next to an open porthole! Cue plenty of jokes about the cleaner leaving the window open when Hoovering, thus bringing about the demise of the high seas fleet.

Back on the boat for a hearty breakfast, and Ian was having problems with the compressor. He decided to head back into Stromness where a mechanic was waiting for him. We were on tenterhooks as to whether there would be further diving for the day, but the compressor was duly fixed and Ian steamed back out to the Karlsruhe. This is a much shallower wreck, a light cruiser well broken up. I had enjoyed it was one of my favourite dives of 2005, and was looking forward to seeing it again. The Karlsruhe was another light cruiser, slightly smaller than the Dresden and Koln, and now lying shallower than the other cruisers in about 25 metres of water. This makes for a lighter dive, and is perfect for a combination of 32% and Oxygen for a really long dive.

Once again, the teams had been moved about, to give everyone experience of diving with one another. I was diving with Howard, and Gareth was diving with Wilbo. Gareth and Wilbo were going to take the scooters in and do circuits of the wreck whilst Howard and I located a suitable entrance and did the usual ferreting. Howard excelled himself, finding a couple of great entrances, that we dutifully explored, although we did not go deep into the wreck as I decided it was a little too broken up and unstable. It definitely seemed to have flattened in the last couple of years since I had first visited, which was very sad. There were several sprung plates that were whole the last time, and the bows had a distinct sag to them which were absent in 2005. This is a real shame. These fantastic wrecks will not be there for ever, and it will be a sad day indeed when they lose their distinctive shapes and start to become flattened piles of plates. Guess that's a while away yet, but it is sad to see it happening.

Gareth and Wilbo managed about 6 circuits of the wreck, having a great time on the scooters, before stowing the scooters and doing their ascent. Howard and I had a slightly different story. Howard's p valve failed, causing a massive suit flood and resulting in him calling the dive immediately. We began an immediate ascent and Howard boogied up to the shallows a little faster than me, in order to get into warmer water. As we were decoing on Oxygen anyway and only had a few minutes’ stops, this was no real drama, but I could see his hands shaking on the ascent, and we if the deco had been any longer we would have cut it short in order to get him to the surface. Back on the surface he practically leapt out of his dry suit and into some dry clothes, and much humour was derived from the cause of the failure :)

Everyone else surfaced with no issues, and everyone had enjoyed themselves. The visibility had dropped to about 5 metres, but it was fairly light in the shallows, a complete contrast to the dark, moody wreck of the Markgraf.

We had a fairly quiet evening, with the final day's diving ahead of us. There was no helium left on the boat, but luckily Just about everyone had a fill left, so we were good to go for the James Barrie. Despite Roy and Mark trying to talk me into deep-airing the Barrie as they had also enjoyed how wasted I became on it, I had decided to do it on mix so I could use ratio deco, and also because I was interested in seeing the wreck with a clear head.

There was a sneaky helium rustling run organised this evening. As the skipper had told us he had run out of Helium, Gareth threw on a twin set and walked over to the MV Valkyrie, where Hazel give him a fill. Sneaking back, he was lumbered by a non-plussed skipper who groaned that he could have done the fill for him as he had 80 bar remaining in one of the J's. In Gareth's defence, the entire boat did hear the skipper say "That's it, no more helium" earlier in the day. Hey ho.

With the plans and teams all organised for the morning, the mixes checked and kit assembled, one half of TFT headed down the pub, whilst the other had an early night. hic.

The Chimps Do Scapa - Part 5

[b]Day 4[/b]
Dive 7: SMS Koenig. 39 Metres. 38 minutes Bottom Time. 24 Minutes Deco Time. 21/35 and 50%
Dive 8: Koln. 36 Metres. 45 Minutes Bottom Time. 15 Minutes Deco Time. 32% and Oxygen

The Koenig is the name vessel of her type. At 580 feet long, with 14 inch plating and displacing over 25 thousand tonnes, these battleships were truly monsters of their time. They were capable of in excess of 20 knots, and carried 10 12 inch guns to impose their will. There are three of these monsters resting at the bottom of Scapa Flow. The Koenig seems to be the least popular of the three, although it rates as one of my favourite wrecks. Today was to be a team Foxturd dive, with Gareth, Howard and I diving together, Wilbo with Roy and Mary and David Soloed. We dived in and descended to 40 metres. The visibility had dropped to approximately 5 metres. The plan for this dive was to penetrate the wreck. We all took reels with us, and searched for a suitable hole. At about 35 metres, we located a blast hole into the wreck, through which we see a variety of passageways and hatches leading further into the wreck. This was precisely the sort of thing we were looking for, so we did a flow check and calculated appropriate gas restrictions before I tied off a primary and secondary tie and started lining into the wreck. We swam for about 15 minutes, tying off wherever possible, and gradually made our way further and further into the wreck. The murky viz became clearer as we reached part of the wreck that were obviously less frequently visited, although the bottom of the corridor we were in was covered in a deep layer of rust that had fallen down and settled from the levels above. All too soon, we reached our turn pressure, and I called the dive. We turned around and began to collect the tie-offs, making our way out of the wreck. This was putting the Tech1 stuff into real practice, and we all loved it :)

Back outside the wreck, we tidied up the reel and swam slowly along the wreck, past casement gun after casement gun. There were several large blast holes leading into the wreck that looked very tempting, and everything was covered with a patina of sea life, but we did not have the gas to linger too long. Having racked up about 45 minutes on the wreck, we drifted slowly upwards along the hull until we were swimming about on the top of the wreck. We called the dive and began the 25 minutes of deco I was calling. Howard whinged about the amount of deco because his magic machine told him the average depth was shallower than I had estimated it. However, I told him to quite whinging and put up with it until it was his turn to call the deco :). The deco was uneventful, and we hit the surface on schedule. Back on the boat for surface, and a hearty breakfast, and a surface interval resting off Lyness before going in for the second dive of the day, the Koln.

The Koln is s very different story to the Koenig. It is one of the smaller cruisers, although well equipped for her time. She was bristling with guns and capable of laying mines. She had thick plating for her size, and was capable of an amazing 29 knots. Unfortunately, she is now fairly well broken up, so there are plenty of opportunities for swim throughs and wreck penetration if conditions allow. The teams had been rearranged so that Howard and I were diving together. Now this is always a little dangerous. If you consider me to be the "middle" member of team Foxturd in terms of caution, Gareth is the angel on my left shoulder, and Howard is the anti-Christ on my right shoulder. When all three of us are diving together, there seems to be a natural balance between caution and adventure. Remove Gareth from the equation and it all goes horribly wrong. All of a sudden the little evil whispers in my ear from Howard seem very tempting, and things can get a little crazy.

Sooooo, Howard and I jumped din together with the intention of spending the entire dive inside the wreck. With scooters. What could possibly go wrong?

Actually, nothing. We had a stunning dive, and all the lining in was done according to Mr Kerslake's beasting, slowly and carefully, with the line tight and secure. We located an appropriate hole and secured the scooters outside the wreck. We then lined in for maybe 5 minutes before we located a hatchway that led deeper in the wreck. We were placing tie-offs every few metres, but the visibility warranted it. Lining in like this is a slow process, but we lined in for maybe 15 minutes before turning around and coming out again. We went further into any wreck than I have been before, and it was amazing to see parts of the wreck that have not seen daylight for 90 years. Deeper inside the wreck, things become a little more preserved, and ladders and companionways are more obviously recognisable. There is more rust and sediment, as it is not disturbed, and you have to be careful as a poor fin stroke can turn 5 metres of visibility into 0. We had a fantastic time, and I could hear Howard's calm slow breathing behind me, and see his torch signals in my line of sight, so everything was well with the world. The way out was much faster, with Howard pulling off the tie -ins for me and keeping the line tight as I reeled in the line as fast as possible. Back outside the wreck and Howard and I were laughing our heads off with the fun of it. We stowed the reel and got back on the scooters.

We scootered around a complete circuit of the wreck in a few minutes, passing all the other divers on the boat. We then scootered up to the top of the wreck. Scootering over the top of the hull, we could see some large holes that looked incredibly tempting, but I just did not have the gas to think about it. I called minimum gas and we ascended to do 10 minutes of O2 deco before heading for the surface. Probably the best dive of the week for me, I was smiling all the way through.

Tomorrow was to be another penetration dive, one I was really excited about. Having located, on Monday, the hole in the Markgraf I swam into last year, the three of us were going to swim directly to that hole and penetrate the wreck, to see how far it goes......

The Chimps Do Scapa - Part 4

[b]Day 3[/b]

Dive 5: Freesia. 40 Metres. 38 minutes Bottom Time. 40 Minutes Deco Time. 21/35 and 50%
Dive 6: Hessonite. 40 metres 20 Minutes Bottom Time. 20 Minutes Deco Time. 21/10 and Oxygen

Tuesday was our day for diving outside the flow. We wanted to explore some lesser known wrecks, and experience the visibility that the waters are famous for. The plan was to dive the Freesia, a little known wreck in approximately 40 metres of water. It was originally a 40 metre long trawler, sunk in 1922.

Now, this was a little way outside the flow and frankly, the weather was blowing its nadgers off. I guess the words "Natural protected harbour" didn't really register with us when we said to the skipper "Yeah we're happy to go out". Unfortunately, a later chat with the skipper revealed that he would go out even if a flaming horseman was riding next to the boat screaming" Doomed, you're all doomed" - the invincible will handle far more of a rough seas and the divers will usually bottle it before the boat has any issues. So, off for tha 3 hour steam we went, with the boat rocking and rolling. Remarkably few people were ill, but there were definitely a few people, including myself, who were feeling sub-optimal. One interesting point for me is that we passed right next to the Kitchener memorial, the memorial for the world war one general famous for the "England needs you!" posters, who died when the HMS hampshire he was on in the area struck a mine and sank in 68 metres of water. She is a protected wreck so diving is a no-no, but the history is fascinating, and it seems you can go nowhere in Orkney without an amazing story revealing itself

After a long three hours, I handed over my tech1 card to a disapproving GLOC, grabbed an X-Scooter and jumped in to solo it. It approximately 15 metres I could see the bottom clearly 25 metres below me. At the bottom of the shot line the viz was a good 25-30 metres, the water was blue rather than green, and the sands were white. I can't imagine anything better abroad. I fired up the X-Scooter and began to explore the wreck. It was fairly flat, but it was stunning to be able to see an entire wreck from one position, select where you want to go, fire up the scooter, and just be there. I was having a great laugh, although the other divers on the boat were having a more difficult time, as there was no real slack, and a very noticeable surge at 40 metres. Mary and Roy discovered the telegraph still on the wreck, but we were not equipped to lift it so moved on. There were big brass flanges lying around, enormous boilers, and plates lying on their side. Lots of life, with dead men's fingers, a few congers and lobbies, and a couple of edible crab. There was also a bent prop shaft, with the single blade of a propeller remaining. There were also some small pieces of pottery lying around.

I racked up 30 minutes on the bottom at about 39 metres, which gave me 20 minutes to do. As Gareth and Wilbo had dropped in about the same time as me, I scootered over to them, stowed the scooters, and began the ascent. Deep stops at 27 and 24 metres were followed by a gas switch at 21 metres. I also fired a bag up from 20 minutes of uneventful deco before all three of us broke the surface at the same time. Howard and David had managed to miss the wreck despite having scooters to move them around, and had done a minimum gas ascent 15 minutes earlier, so were available to help everyone get back on the boat.

Everyone was amazed by the light and the visibility, but everyone was also a little tired when they got back own the boat - apart from me. Lesson of the day was that in good visibility, a scooter is definitely a valuable and useful tool. In poor visibility, they are just a waste of time. However, when you can see for a distance on the wreck, and use the scooter as a tool to get you to a point you have already identified, they are superb. They also greatly reduce the working level when you are diving outside slack. I can see the attraction, but I just don't do enough diving in good visibility to warrant getting one.

On to the second dive.....

The second dive was a known wreck in 30-40 metres of water, which had never been located. The wreck was the Hessonite, a fishing trawler sank 80 years ago believed to be in that area, but the precise site of the wreck has never been located. We were happy to do a scenic dive, with the possibility of diving a new wreck. The teams were re-arranged for the second dive, as Gareth and Wilbo wanted to use the scooters. This left Howard and I to dive together. Howard was feeling a little tired after the first dive, so we were going to do excess amounts of O2 deco to clean him up a little at the end of the dive. I got into position at the exit, with Howard just behind me. Unfortunately, he misinterpreted a signal from the skipper and we jumped in for 20 minutes on HMS seabed. Sigh. We descended quickly, again in absolutely stunning visibility. At 35 metres of depth, with a good 6-7 metres below us clearly visible to the seabed, I levelled out - I was breathing 32% and the mix was getting a little hot for going any deeper. Howard levelled out next to me and we had about 20 minutes of drifting over a fairly bland sea. This was completely excess for the type for the dive we did, but it gave Howard some O2 time to liven him up, and I always enjoy O2 deco as it makes me feel all nice :)

Back on the surface we were first up, and in the end we were the lucky ones. All the divers who had been dropped in the right location were swept close the cliffs in quite a swell, and Invincible struggled to get close enough to them to pick them up without them swimming out a little. This meant everyone was pretty wasted by the time they were picked up, with us on the verge of jumping in and towing them out from the cliffs with the scooters. In the end everyone was safely picked up, and to our delight Fiona had cooked up a storm for us to eat. I managed to munch my way through a huge plate of food, and then, as Invincible started the 3 hour steam through a raging sea back to the flow, I said goodnight to everyone, crashed into my pit, and slept like a baby. I woke up three hours later when Ian turned the engine off :)

Plan for the next day was two deco dives, the Koenig and the Koln, another two cracking wrecks. The obligatory fettling began.....

The Chimps Do Scapa - Part 3

[b]Day 2[/b]

Dive 3: SMS Markgraf. 44 Metres. 44 minutes Bottom Time. 45 Minutes Deco Time. 18/45 and 50%
Dive 4: Tabarka. 15 metres, 40 Minutes Bottom Time. 5 Minutes Deco Time. 21/10

We gassed up with 18/45 and 50% for the Markgraf Dive. Wilbo was feeling a little off colour this morning, so decided not to do the Markgraf, but Dave, Gareth, Howard and I were good to go. I kept pretty much to myself whilst getting ready, as I wasn't really in the mood for any banter, just wanting to get the wreck out of the way. I was defintiely a little tense, but did not feel unduly stressed or worked out, so decided to go ahead with the dive. We jumped in and rocketed down the shot line at 20M per minute, forming up as a four when everyone had arrived. We checked gas and time, and then decided over the hull to the seabed. We swam along the wreck, which was in good visibility but very dark, until we reached the stern, with the massive rudder still in place and very impressive. I wanted to find the hole I had swam into the previous year, which was up at the bows at the opposite side of the wreck, so we got into line and boogied along the entire length of the wreck, going through some really cool swim -throughs on the way and passing other dives, including Roy and Mary, who whose lights could be seen deep inside the wreck. They were obviously enjoying themselves :)

Reaching the bows, we stopped for a few minutes whilst Gareth took some great pictures, and the bows were a great sight disappearing into the gloom. The bows on the Markgraf are probably the best preserved of the three battleships at scapa. We lingered for only a few minutes, as I was really keen to find the hole. And find it we did. We swam along the side of the wreck and after about 2 minutes I saw a massive opening. I signalled to Dave to hold position whilst I investigated. There was an overlap of plates, so you could swim "along" the wreck, but actually just inside it, for nearly 7-8 metres, before the hole went black and became a solid wall. Just before the end of this passageway, there was an opening that led into the wreck which just opened into a massive space. I could see immediately that I had been here fore. The hole "in" must have been where I managed to swim deeper into the wreck in my panic to get out. Of course, in decent visibility, it was all too obvious how JW and I had done what we did - anyone could have. I wanted to investigate the deeper hole further, but decided that today was not the day for lining into this hole, as I had discussed this in advance with the team, and we were nearing the planned end of the bottom time. I had satisfied myself that I had put my demons to rest and the wreck no longer held any nervousness for me, so I put this down as a great dive. The plan would be to come back later in the week at which point I would line into this hole and investigate it, as on trimix it looked really interesting rather than frightening!.

When I came out of the hole and greeted the team, we were a minute or so away from calling the dive anyway, so I thumbed it. We broke into two teams of 2, with GLOC calculating the deco for one team and me running the numbers for the other team. There was a smooth ascent to 21, at which point a bag went up from either team and then we began the 30 minutes of deco. We hit the surface, at which point Howard announced he wasn't surprised people get lost in there, as it was bloody massive and dark. I went great. I had faced my demons, and the Markgraf had turned from something I had been somewhat apprehensive of, into one of my favourite wreck dives. I couldn't wait to go back later in the week.

In addition to TFT, everyone on the boat had a successful dive. Roy and Mary had spent much of their time actually inside the Markgraf, and enjoyed themselves thoroughly. Once everyone was back safely on board, we steamed off towards the Tabarka, as the wind, as promised by the skipper, had indeed died down, and conditions were improving. We did make one change to the planned week, with a decision to dive outside the flow for just one day. With the weather being so changeable, we didn't fancy risking two days being blown out, so agreed with the skipper to dive the Freesia and Tommeline, at 40 and 30 metres respectively.

The plan for the afternoon was the Tabarka.

The Tabarka was a 2624 ton steamer sunk in Burra sound as a block ship. Today, all the planking has rotten away, but the structure of the ship remains - making for a fascinating dive. Added to the open structure, the area is reknowned for it's good visibility as the flow washes the wreck through and keeps the area mercifully free of silt. This is a stunning wreck in good viz. Last year we were unfortunately forced to dive it in almost nil visibility, which removed much of the grandeur of this amazing swim through, so we really had no idea what to expect this time. This is a negative entry dive as you don't have time to mince about the surface unless you fancy diving in the shipping lanes. Or the Atlantic Ocean. So it's suck the air out of you wing, deflate your suit, and then jump in as a 12. Then get down as fast as you can to the wreck before the current takes you past it and you slam into the Doyle like wile. e. coyote. This time, when we jumped in, we could see the wreck from the surface 13 metres below us. niceeeeee. When we got down to the wreck, I immediately found an opening, and then barrelled into the wreck to get out of the current. The rest of Team Clone followed inside and we then separated into a team of two and a team of three and began exploring the wreck. The visibility was about 20-25 metres on the horizontal, and the wreck was as stunning as usual. It was a little diver soup at the beginning, but soon thinned out as people found holes to explore. I managed to weasel myself into the propeller shaft and swam along it, which was great fun. There was one part I struggled to get through, until Dave came up behind me and basically shoved me into the hole. For those that have not dived the Tabarka, this has to be one of the best wrecks in the UK. It is essentially one massive swim through, where you can see sunlight filtering through the ribs of the wreck, enormous boilers and engine room with easy access. It's basically wreck penetration for dummies, as everything is well open and accessible. It's tremendous fun, and always a highlight of a week in scapa.

Everyone had a great time, and after about 30 minutes of slack things started to pick up so we canned it. I bagged up for Dave and I and we did a nice slow ascent, covering a massive amount of ground in the ever increasing pace of the current. You could see everyone had had a great time by the smiles on the boat when everyone was dekitting. A very successful day. The next day, we were due to go out of the flow, so after a fairly pleasant meal unfortunately served by the dimmest and least experienced waitress in the universe, we decided to call it a night and head back to the boat. Howard surprised me with a cigar and malt whisky to celebrate our diving the Markgraf, which was very civilised, and then we analysed the gases and assembled out kit before calling it s night.

The Chimps Do Scapa - Part 2

[b]Day 1[/b]
Dive 1: Kronprinz WIlhelm. 36 Metres. 45 minutes Bottom Time. 30 Minutes Deco Time. 18/45 and 50%
Dive 2: F2 and Barge and Bottle Run. 40 Minutes Bottom Time. 5 Minutes Deco Time. 21/10 and Stage of 32%


As usual, I was up and about at 0530, never been one for sleeping in. I went outside to see what the weather was doing at 6am and got quite a surprise. In most of the UK, we fail to recognise how lucky we are with the weather. It can be "a bit rainy", "a little overcast", or in extreme cases, "not very pleasant". In Orkney, when you open the door in the morning, the weather kicks you in the balls and headbuts you as you fall over. It then mocks you as you beg for mercy and stomps away back over the hills with the knowledge of a job well done. The weather here is strange. It can be blowing it's nadgers off one moment, and perfectly calm the next. This was the case this morning. A beautiful sunrise was interspaced with the occasional howling gale.

The skipper arrived at 0730 and we discussed the plan. He told me the weather was looking like a gale force 8. I was disheartened by this, but he assured me that this doesn't really bother the invincible, and the divers would bottle out before the boat would, so the plan was still on to do the Kronprinz. We kitted up as the boat steamed towards the big German Wrecks. No-one managed to leave themselves tied to the boat, but there was one close call, with Wilbo managing to get within 2 feet of the ladder before Fiona whispered that most divers traditionally take their fins with them when they go diving. Whoops. Things were to get no better for Wilbo on the second dive when GLOC told him that although ratio deco required no complicated dive computers, timers and depth gauges were certainly approved in the DIR ethos, and some people actually considered them fairly important to the process of calculating deco.

For those that have not been to Scapa, the Kronprinz is a World War One era battleship, the pride of the German High Seas Fleet. At 28,500 tons in weight and 575 feet in length, she was armed to the teeth with 12" guns and armoured with 12" plating. Due to the weight of her turrets (600 tons a piece) she turned over when she was scuttled and came to rest upside down on the seabed some 38 metres below. There are numerous blast holes in the hull to explore, and one can view the superstructure, main and side armaments and plenty more if you descend to the seabed and swim along the length of the ship.

The Kronprinz blessed us with about 8 metres of Viz, more than enough, especially as we had 1 metre when I dived it last year. This made for a very pleasant dive, although Dave struggled with being underweighted throughout the dive, which added to his stress levels and was noticeable in the amount of gas he consumed during the dive. The wreck is superb, and we got a good view of the 12 inch guns under the plating, on two enormous turrets. Once again, I found the sheer thickness of the armour plating lying around simply staggering, amazing when you compare this with the paper thin materials used in modern warships. These were not modern ships with high tech intelligent weaponry. These were clearly ships designed simply to both give, and absorb, enormous kinetic wallops, until one of them gave up. When compared with the almost flat rubble that makes up many of the wrecks off the South coast, these wrecks, with their 10-15 metres of imposing height above the seabed, are simply stunning.

We had a great dive, and I ran ratio deco for Dave and I. This is simple on the big ships, as you simply swim up the hull and go from 38 metres up to the 21 metre stop - still on the hull of the wreck. By he time we hit 6 metres, we could see the sea rocking and rolling above us with the heavy swell, and I could certainly feel the SMB wanting to get away from me. Because of this, we decided not to dwell too long in the shallows and got up as fast as was safely possible. The boat picked us up nice and quickly as usual. We were first up, due to Dave discomfort during the dive, so we were able to assist everyone else as they got back on the boat. The climb up Invincible's ladder can be a pain when the sea is a bit lively. Today is was a bit lively to the tune of gale force 8.

Diane got back on the boat with a grim look on her face. The neck seal had held well, but the wrist seals were "sub-optimal" - they would be redone later. Adding to the list of failed equipment was a ripped wrist seal for Nick, and a holed suit for Roy. Everyone was getting wet in the cold, but seemed to be grinning and bearing it.

The Tabarka was blown out; the skipper reckoned it would be daft to try it in the force 8 gale that was now blowing. However, the F2 and barge would be fine as it would be a little more sheltered.

The F2 was a German WW2 escort vessel. She was 249 feet in length and weighed 790 tons. She sank near Lyness in 1946. In the 1960's, a barge was being used in the salvage of the F2. Some of the machine guns from the F2 had been transferred when the barge sank right next to the F2 in a storm. Now they make an interesting double wreck, with the advantage of the fact that a diver can drift off the wrecks and onto the bottle run, an area of the flow where countless naval ships had been tied up over two world wars, and as a result the seabed is littered with detritus thrown overboard from these ships.

Dave and I jumped in on a 15 metre dive with full twin sets and a stage as well. We had a great dive, the F2 was absolutely covered in sea life, and we spent nearly half an hour inside the barge ferreting around the machine guns lying around inside. The barge is quite open and makes for a good ferret around. We watched Gareth taking photos and Howard and Wilbo playing hooligans on their scooters for a while, and the decided to leave the wrecks. We then drifted onto the bottle run and spent ages digging around. We found some great bottles to be taken home and cleaned up, and Dave kept finding abandoned dive kit, which he dutifully put in his goodie bag to clear the sea floor. He also picked up a massive lobster and a massive crab, but let them go as we had no real way of cooking them, so there was no point taking them up. We were both giggling away during the dive, having a great time. We ran up a runtime of 90 odd minutes and then called it a day as we were starting to get cold.

Back on the boat, we were the last up this time, so everyone was around to help us bring our swag back on the boat. That evening, there followed a MASSIVE fettling session. Several suits were repaired, various seals were repaired, a torch battery, and various cheaper items! No-one had dropped anything yet, but the kit seemed to be starting to self destruct! Luckily, Stromness has plenty of beer, so half the team got shitfaced whilst the other sorted out the kit and gas for the following day. Sigh.

There were two "dumb shit" moments. GLOC managed to completely bork the deco, and cut the deco two minutes short without realising it. He felt shit about it, but we had a good natter and worked our where the error had been made. Lessons learned. Dianne took the blue ribbon prize for the "dumb shit" award, by leaving a burning candle in a wooden cabin with the curtains fluttering, whilst she went for a shower. Luckily, David wandered past and wondered what the flame was for, and promptly blew it out. Doh. Everyone had a good laugh in the evening.

The plan fore the next day was something I had been waiting for. The Markgraf. We had decided to re-arrange the team for this. Gareth, David and Myself would dive as a 3, and Howard and Wilbo would dive as a 2. In the afternoon, we were planning to dive the Tabarka. This is perhaps my favourite wreck dive, so with the weather forecast suggesting that the wind and rain were going to die down by the morning; this was shaping up to be an interesting day indeed.

The Chimps Do Scapa - Part 1

[B]Part One....[/B]

The Go with the Flow 2007 Tour Trip Report

the chimps all arrived at my house on Thursday evening, to be greeted with an evening meal cooked by the fair hand of my good lady wife, and two cars to pack. We loaded the cars at my house at 10pm on the Sunday, and it was touch and go as to whether we are going to have to take three cars. As it was we had to leave 5 stages behind, leaving only ten for the 5 of us to share. We all then decided to get an early night. I checked the spare room carefully, but despite apparently drilling through the walls all night with a hammer drill, there appeared to be no damage to the room Howard was in. We could not understand it, but jumped in the cars at 0430 and began the long trip up to Scotland

The trip up to Scrabster was, as you can imagine, a riot with all the chimps in tow. Howard's car was "dragging it's arse up the motorway like a dog with worms". Gareth's was not a great deal better, and had all the acceleration of an asthmatic ant with some heavy shopping. It was especially slow when Gareth was actually driving it, and speeded up considerably when someone else got behind the wheel. Howard, as usual was driving like someone had set fire to his arse, and we made good progress throughout the day. The banter was flowing thick and fast, as was the coffee to keep us conscious after the 4am start. Travelling up to Scrabster usually forms part of the holiday, as it's a good laugh, but it is a hell of a way, 718 miles and 13 hours.

We arrived in Scrabster, where I had booked us all into the ferry inn for the night before the ferry. This turned out to be one of my better decisions as we all managed to get shitfaced with only a 1 minute walk to the Ferry in the morning. Closely following us, Diane (Ms Diane, Lady Di, Chimp Bitch) arrived shortly after, followed by the Two Nics. A fairly heavy drinking session ensued, which give that neither Dave nor I are heavy drinkers, rapidly became quite messy.....

In the morning, we all had a great breakfast, with the exception of Howard, who had spent the night apparently drilling into the walls again.

We arrived at the ferry terminal in plenty of time to greet the people from week one. I was particularly looking forward to us. We bumped into SteveS who assured us that the week1 group had had a great time, with good viz. The two groups on the boat had kept largely to themselves so there was little unpleasant politics. 3 of the week1 group had decided to bail early and gone home on the Friday night ferry, depriving us of the ability to ask them how they got on. Never mind, eh. The ferry across from Scrabster was a little lively. It was as windy as I had seen it, and the skipper of the ferry apparently agreed as he didn't go past the old man of Hoy to my disappointment, but rather went through the flow itself, past Lyness and up towards Stromness this way. As we went past the entrance to the flow, we could see the carnage out in the open sea and decided the skipper was probably wise. The chimps were getting a little out of control on the ferry - we all have a form of primate attention deficit disorder. Luckily, Diane provided a variety of toys and games, which kept the chimps quiet and out of trouble; at least until they figured out that they couldn't eat, fight or have sex with any of the toys provided. Then, once again, chimp induced carnage ensued. After giving all of toys with pure altruism, Di was rewarded with the words "are you going to take all this shit with you, or leave it here".

The weather, frankly, was appalling. Driving rain and a serious wind. Ian the skipper was there ready to greet us, and watched in amused bewilderment as we proceeded to unload a phenomenal amount of kit. 12 divers on the boat, with 20 twin sets and Christ knows how many stages and oxygen bottles. We got all the kit stowed away, and began the traditional mad fettling session. Some amusing highlights were GLOC pouring the water out of his Argon bottle prior to deciding to run his suit off his stage bottle instead, and Markosis compensating for ill-fitting twin set bands with rubber bands and duct tape. Diane was genuinely upset that someone pointed at a stage with a suicide clip on it and asked if it was hers.

One moment that amused me was collecting the "in case of emergency" forms provided by the skipper to be filled out by us all. On Gareth's some subtle editing had added the words "unfeasibly small penis" to his lists of distinguishing marks. Howard's could not be edited by the author of this piece, as he had already filled out his form with the words "my drowned and bloated carcass could be identified by my enormous schram, red and scarred".

The mandatory trips to Scapa Scuba were made to pick up low pressure hoses, fix Howard's dry suit, and pick up various shiny things. Dave and I then settled down to complete the main task of the evening, which was to change the wrist and neck seals on Diane's suit. This turned into a bit of a drama as the neck seal was a swine to get off, but the wrist seals amusing "popped off" with almost no effort, leaving no residual glue anywhere, which I found a little worrying. Howard's Salvo promptly committed suicide as the battery cables snapped off. Scapa Scuba essentially refused to touch, so Dave set about it with a soldering iron, a blow torch and a nail. Howard looked worried...

The Minnerva

Text by Chimp 5

I don't get to go Trimix diving as much as I'd like so was recently delighted when the Foxturd guys agreed to my request to become an Honorary Chimp and go diving with them. They went one better and have made me a full chimp with the designation "5" This trip was the first time we'd go sea diving although we have dived in quarries before.

The Minerva was a long ride in the boat in the sort of sea that's on the edge of being uncomfortable but Smudge's boat, the Scimitar made light work of the seas and we arrived at the site in a little over 2 hours. Finding slack was a bit difficult which resulted in us being ready for longer than I would have liked, fully kitted up, in the sun and with a rolling boat is not the most fun, but diving is like that sometimes, I guess.

Garf, Gloc and I hit the water and got to the shot. I was to be number 1 (so they could both keep an eye on me I expect ) and set off down the shot. This was hard work in the current and I took longer than would have been ideal. We eventually arrived at the wreck and took a moment to settle and sort things out, then set off on a tour. Along the way we saw several fish, crabs and the occasional lobster till we arrived at the bow so we turned and headed back towards the stern. Near the stern was a nice little swim through the back along the starboard rail area. Garf spotted a really nice jelly fish. The number of HID lights at times gave the wreck the feeling of being a War of the Worlds set

I knew I was nearly at minimum gas and was about to check when the dive was thumbed so we headed of for a largely uneventful deco run by Garf, I shot the bag, although at times the current carried us along for a bit, then stopped before taking us away again. It was disconcerting in a mild way to see the string heading up to the surface at an angle of 45degrees.

For a whole bunch of reasons we decided that was enough diving for the day so headed back to Weymouth. We met up with Howard Payne, David Stern and some of Howard's club for the evening and had a top meal and continued the rich vein of banter that had punctuated the day already.

A huge thank you to Smudge & Helena for making us feel very welcome, to Marianne (MJH) for organising the gig and to my fellow chimps for having me.

I look forward to the photos imminently

Taking Underwater Pictures

Some of you who frequent this blog may have noticed that I do a little underwater photography and I thought I would pass on some thoughts about how to get the most out of being underwater and taking pictures.

First off, other than you have a camera, you are underwater, and the normal laws of physics apply underwater, there is little in common between underwater photography and topside photography! The main point to note is that underwater photography in the UK means a lack of light. The human eye is incredible in compensating for reduced light levels and it is only when you look through the viewfinder do you notice that the shutter speed of 1/60 at 15m has now dropped to 1/4 at 25m! In addition to this, the eye compensates for colour reduction without realising it too, and it is only when the image is reviewed on the surface do you note that the colour is gone!

Equipment

Last January I was going on a trip to Tenerife and although I had 10 years plus of topside photography I had never taken a camera underwater, and I wanted to start. After researching the idea, I had my heart set on an Ikelite rig for my S2. After totting up the costs I realised that spending over 2 grand on something I might not like or enjoy was pretty daft, so bought an Olympus 5050 with Epoque 0.56 WA adaptor from Alan James Photography in Bristol. I then spent the rest of 2006 using this rig with some pretty good results. After I started doing more deep stuff, and also taking pictures of friends scootering around, I was seriously hankering for a housing for my S2. £350 later from Belgium my Aquatica housing arrived. £500 later I had an 8” dome port, gears and extensions. Another £1000 got me my 2 x Ikelite SS200 strobes from the USA plus some ULC buoyant arms from Cameras Underwater in London. The new rig now weighs somewhere in the region of 10kg on the surface and -1kg in the water.

If you are starting out in underwater photography and you own an SLR, I would personally hold off being a housing for your SLR until you have got your buoyancy nailed and you are used to using a camera underwater whilst maintaining awareness of your buddy, your environment and your gas. If you have got this nailed and you have £3k to spare, go and buy an underwater housing for your SLR, you won’t look back.

Basic Techniques

The most important bit is to get as much light as possible. Most of the shots that I have taken so far have been without strobes and so I have relied on natural light. Using the Olympus 5050, I could take advantage of the f1.8 lens and 200ISO to get the most out of the shots. Move to 400ISO and the image is very grainy and can only really be viewed in mono. Using the SLR I don’t have lenses which are as fast (the 10-20mm max aperture if f.35) but the noise levels in the shots are far less and therefore I can shoot about the same shutter speed but have a much larger and cleaner image. Whereas I would struggle to get a useable shot at 400ISO on the Olympus, the S2 at 1600ISO is perfectly acceptable for wreck/technical diving type images. If I wanted to get finer detail I would use a strobe and bring the ISO down to 100.

Another issue that is linked to light levels and depth is colour loss. Once you are past around 10m, images become very green and you need either a strobe or torch light to bring the colours back. Alternatively if the image is too green but you have sorted the balance out, then you can convert to mono which is what I do with a lot of my images. There are 2 ways to compensate for this colour shift if you do not have strobes; the first is to white balance the camera before you take the shot using a something which is white and ‘fooling’ the camera that this green tinted white surface is in fact white, the second method is to shoot in RAW which means the camera stores all the information but doesn’t have any final image, this is done in computer software topside.

If you are shooting natural light, always try to shoot down light such that it is over your shoulder into the subject’s face. As I said above, your eyes are very good at compensating and so if you shoot into sun the image will just show a big shadow from the areas being shaded as can be seen in this shot below; I really needed a strobe for this shot.

Photoshop Techniques

As I said above there is an issue with colour shift towards green when in UK waters. This means that the red and blue are absorbed quicker than the green, leaving you with a green image. There are some techniques which you can use in Photoshop to counter this. First off, shoot RAW and then use the grey scale dipper to get a neutral grey. This will get you very close to where you need to be and then you can play with levels after that. Otherwise, you can use the ‘Levels’ tool which can be found in most photo imaging programmes and adjust the light levels across the image. The following example uses PS CS for screenshots.

All levels.jpg, this is the original file. Taken in 15m at NDAC, Chepstow. As you can see this is quite green and fairly low contrast. This shot was taken at about 2m camera to subject.

Bring the black point (left hand arrow) and white point (right arrow) in until they meet the histogram. A histogram shows the dispersion of light quantities over differing intensities and colour channels. Here we are looking at the red channel, left is pure red, right is pure white (if this was all-levels, the left would be pure black). What we are trying to do here is make what light we have fill the whole spectrum. In the red channel you can see there is a lot of light missing, so we need to spread the light levels across and pick up the lost dark red.

Red Levels

Green Levels

Blue Levels

As you can see, as you spread the available light across the full spectrum, the image starts to get its full colour back again. However, the image is still a little flat so we add some contrast using the curve tool.

This makes the darker bits darker and the lighter bits lighter, the human eye likes contrast as it makes it easier to define edges and shapes.

RAW Images

This is what you can do with RAW images and why I will now always shoot photos in RAW if I can!

If you have any questions regarding my underwater photography or if you want some tips or help, drop me an email via my website which is listed at the top of this blog on the right handside.

New Member Joins Team

Mal Bridgeman has joined Team foxturd, as he wants to get more trimix diving in. As honarary chimp, his duties will consist of ensuring banana stock never runs too low, and also ensuring Howard makes it to the divesite on time now and again.

Anyway, we welcome him to the team. Mal is an instructor and trimix diver, and I'm sure we will all be learning from each other in the near future.

so welcome!

Tech1 Ratio Deco - Explained

Ratio Deco at the Tech1 Level.

Firstly, a few caveats. I have put some thought into all of this so please don't skip them. I expect they will be obvious to everyone on YD, but perhaps not to the person who googles Ratio Deco and stumbles across this post.

1. This post does not represent Ratio Deco as taught by GUE, FifthD or indeed any other agency. It is my interpretation of what I have been taught. Thus, any errors are my own.
2. Ratio Deco usually forms only a small part of a larger course and requires a rounded grasp of specific skills that allow Ratio Deco to be utilised safely. Thus, before using Ratio Deco I can only recommend you seek such training. Please do not dive the profiles suggested in this post without undertaking such training. You could end up hurt or dead.
3. Ratio Deco works in conjuction with a specific set of variables. There are no rules, only guidelines. Use them at your peril.

A few myths dealt with

It's mystic sorcery and "secret" information - well it aint anymore if it ever was
It's complicated - keep reading, it's so simple it's dissapointing once you learn it!
It requires lots of training - The skills required to handle RD do take time to learn. RD itself takes about 15 minutes on Tech1

OK. Now that's out of the way, are you all sitting comfortably, good, then I'll begin....

Has anyone read AndrewG's article on Ratio Deco? The man may be a diving God, and may no more about decompression than most people on the planet, but by God he's a terrible writer. Or perhaps I am simply insulting him and it's written in a such a fashion to enocurage people to take courses and have the concepts clearly explained. The only documentation on RD I have been able to find on the web has been obfuscated by crepuscular logic and an involute style which, frankly, gets on my tits. I thought it might be useful to post some information about ratio Deco that demystifies it, and allows for a more informed debate and discussion on the topic.

So, what is Ratio Deco.

Garf's Definition - the Wordy one

Ratio Deco is defined as being a set of rules that allow an individual or team to calculate the amount of mandatory deco and ascent rates based on the average depth they have been at and the length of time they have been at the bottom.

Garf's defintion - The easy one

If we know how deep we are and how long we've been there we can work out the deco on the way up in our heads without the need of a computer.

"Ratio" refers to the fact that, for a given depth, there is a ratio between the length of time a diver spends on the bottom portion of a dive and the amount of decompression they will have to do on the way to the surface. "Deco" refers to the fact that this process is managing the ascent portion of the dive, including all deep stops, ascent rates, and shallow stops.

Other definitions

"Bottom Time" - The time that passes from the time we arrive at the bottom to the time we leave the bottom. Notice does not include the descent portion of the dive.

"Bottom Gas" - 21/35 or 18/45 Only. The two are interchangeable and the decompression required stays the same. Handy huh

"Decompression Gas" - 50% Only.


The Pre-requisites

In order to make Ratio Deco work for us, there are a number of things we need to be able to do, and a few things we must have with us.

Firstly, we need to be able to control our rate of ascent. I don't mean stop ourselves from rocketing to the surface, although that's a handy skill. I mean we need to be able to change our rate of ascent on demand. For Tech1 level diving, we need to be able to ascent at a constant 3 metres per minute where necessary, 6 metres per minute where necessary and 9 metres per minute where necessary. If we cannot do any of that, don't go near Ratio Deco.

Secondly, we need to have with us standard gases. The ratio deco I am going to explain in this post works when we use either 21/35 or 18/45 as backgas and 50% as deco gas. And that's it. Mess up the standard gases, and it all goes to ratshit. With some confidence and experience behind you, you could alter the deco to compensate, but I am a long way from that in my diving and for the sake of simplicity and safety let's just say that the standard gases are the rule. There are other standard backgases, and other standard decompression mixes, but we are not interested in them at the Tech1 level.

Thirdly, we need to understand something of the limitations. During the course of this post, I am going to explain that Ratio Deco is anot a rigid set of rules, but needs to be adjusted based on variables such as depth. For the sake of this post, I am going to say that the guidelines I give out are good to 48 metres and 40 minutes. Deeper or longer than that and the ratio we are going to use starts to become a little wooly, and needs to be adjusted until we reach the next "set point", which I shall explain in a moment.

Concept One : The Set Point: Calculating Decompression Required.

forget about Rebreathers, this is a different type of set point. The set point is the starting point for calculating Ratio Deco. At the tech1 level, we use 45Metres as the set point. As you increase in knowledge, you may use 66M as a set point and so on.

So, for Tech1, we use 45M. At this set point, we assume that there is a 1:1 Ratio between bottom time and decompression. That means for every minute we spend on the bottom, we spend a minute decompressing. There, wasn't that nice and simple. Minute on the Wreck, minute going up. easy.

Now, there are other Ratios. for example at 66 metres, the gases all change and the ratio is 2:1. for every minute on the wreck we need to do 2 minutes deco. Now I'm not going to get into that here becuase, frankly, I'm not trained to do it.

Let's go back to our 1:1 ratio at 45M. We do a 30 minute dive to 45M (average depth), we need to do 30 minutes decompression. Nice. However, what if our average depth was greater or less than 45M. Well for every 3 metres (or part) shallower than the plan, we take 5 minutes off the deco. for every 3 metres (or part) we add 5 minutes.

So, calculating the amount of decompression we need to do is very simple indeed. Look at the average depth and the time, and compare to 45 Metres.

Example 1: 38 metres for 40 minutes - We're 2 lots of three away from 45 (rounded down) so it must be 10 minutes less than 40 - 30 minutes.
Example 2: 47 metres for 25 minutes - We're above the 45M setpoint by part of a three so it must be 5 minutes more than 25 - 30 minutes.

So, you can see that it's very easy indeed to calculate the decompression in the 30 to 48 metre range. It get's a little more complicated if you go deeper as you are moving between the 1:1 Ratio at 45 metres and the 2:1 ratio at 66 metres, so the question arises of what do you do in the middle. That is a question I sort of know the answer to, but am not qualified to post, and it's outside the scope of what I want to cover in this post anyway. Let's stay at 48M or below to keep things nice and simple.


Portions of the Dive.

Let's go back to our 30 minute dive to 45 Metres. We now know that we have 30 minutes decompression to do on the way up, but how do we do it. Where do we do our stops, and how long should each stop be.

Well, the areas of the dive can be broken down as follows;

Bottom to 80% of Average ATAS = Lower Portion of Ascent.
80% of ATAs to 21M = Deep Stops
21 metres = Gas switch
21M - 9M = Intermediate Stops
6M - surface = Shallow Stops

Or, just for Janos, a pretty chart...

Now, let's deal with each portion of the ascent in turn.

Bottom Portion of Ascent

At this point, we are still ongassing. So, there's no reason to hang about with slow ascent rates. We use 9 metres per minute as it's quick enough to get us out of dodge, but slow enough so it can be brought to a stop comfortably. We want to get up to 80% of our ATAS at 9 metres per minute because if we do it any slower then we are going to bugger up our decompression by ongassing too much. It is critical at this point not to hang about. Once the decision is made to leave the bottom, we leave.

We need to get up to 80% of our ATAS before anything changes. Why 80%. Becuase it's around this area that we stop ongassing and start off gassing. Now, as with everything in DIR, it's not perfect for all oaccassions, but it's about the best standard you can apply to all situations, which is really what the entire concept of DIR is all about. so 80% of our ATAS. How the hell do we work that out. Sounds complicated. Here's the trick...

Let's say we're our average depth was 45 metres. convert that to ATAS =5.5. divide by ten = 0.55. Mutiply by 2 = 1.1. Take that off the depth in metres. 45 Metres - 1.1 ATAS = 34 metres. So, 80% of the ATAS when we have been diving to 45 Metres is 34 metres.

Let's do another example. We've been to 42 metres. Thats 5.2 ATAS. Multiply by 2 = 10.4. Call it 11. Take that off the depth in metres. 42 - 1.1 ATA (11m) = 31 metres.

Repeat that above excercise a few times and you'll find you can do it in a heartbeat without thinking about it, and it's the most complicated bit of maths we have to do in the whole excercise.

Now, just to make things a tad more complicated, we always round to the nearest three, becuase then it's a bloody doddle to do 3 metres per minute up to 21M. So if our 80% is at 34M, we'd actually go up to 33. If our 80% was actually 31 metres then we'd stop at 30M. See how that works?

So, taking our 30 minute dive to 45 metres. We leave the bottom after 30 minutes and we ascend at a rate of 9 metres per minute until we hit 33 metres. This probably takes us about 75 seconds.

Deep Stops Portion of Ascent

OK, so we hit 33 metres and we are now in the deep stops portion of the ascent. At the Tech1 level, this is simple. We do 1 minute stops every three metres. Looking at this another way, we can just do 15 seconds move, 15 seconds stop, which looking at it yet another way, could be done as a 6 metre per minute ascent, which is actually what we do. So all we have to do at this point in the dive is slow down from 9 metres per minute to 6 metres per minute, and then ascend at that rate until we hit 21 metres.

Now, this is an area where I could go on for ever more. The deep stops change if you go beyond Tech1 levels, and all of a sudden the maths gets a little more complicated with longer stops and changing ascent rates, but that's for another day. On our nice, simple 30 minute dive to 45 metres, all we have to do is slow down the ascent rate until we hit 21 metres.

21 Metres - the Gas Switch and first intermediate stop

21 metres is where the work begins. Here we have to switch the team from their back gas onto the decompression gas of 50%. We also need to put up a bag, and work out how much deco we have to do.

Let's get going. The gas switch. The procedure for that is another post, and I never would have believed this until trained to do it, but switching the entire team from backgas to decompression gas takes about 10 seconds. Backgas regulators are clipped off. Now, the roles come into play. Typically one person sends up a bag from 21 whilst another person is running the deco.

The first intermediate stop depth is 21 metres, however we stop at 21M for at least 3 minutes regardless of how much decompression is actually required. why do we do this. We do this to open the Oxygen Window. Now, I've read and know at least 4 different versions of what the words "Oxygen Window" actually mean, but all of them seem to agree that it's not a bad idea to spend at least 2-3 minutes at the depth where you switch to your decompression gas containing a higher partial pressure of O2. Obviously, several compartments are still ongassing, and also you have a limited gas supply, so you don;t want to stay there forever, but 3 minutes as a minimum for Ratio Deco as I am explaining it.

Shaping the Decompression Curve - Intermediate Stops.

Ahh, Howard it putting up the bag, I'd better work out what deco we are going to do before he finishes or he'll only take the piss. Well, we did 30 minutes at 45 metres. That means we have 30 minutes of Decompression to do. so where do we do it

Well, we need to do half our decompression in the intermediate stops, and half in the shallow stops.

Let's take our dive, 30 minutes at 45 metres. We have 30 minutes of decompression to do. that means we have to do 15 minutes at 21-9 metres (see table 2) and 15 minutes at 6-0 metres (see table 2).

Now, our intermediate stops are alwasy the same. They are

21M
18M
15M
12M
9M

That means we have five stops to do. If 50% of our deco is therefore divisible by 5, it's simple. We have 15 minutes to do in the intermediate stops. So we would do the following

21M - 3 minutes
18M - 3 minutes
15M - 3 minutes
12M - 3 minutes
9M - 3 minutes

Now how bloody simple is that.

There is an endless debate about whether you should do a linear curve as I have described above, or whether you should minimise the stops in the middle and load the start and end. This would mean you maximise the deco from the partial pressure of 50% and then start to push the gradient, and ignore the stuff in the middle. This becomes more apparant when the deco is NOT divisible by 5, becuase then the divers have a choice about where to do the stops.

Let's look at a few examples of that.

Let's say we have 18 minutes to do in the intermediate portion. I'd probably do

21M - 4 minutes
18M - 4 minutes
15M - 2 minutes
12M - 4 minutes
9M - 4 minutes

but we could also do

21M - 4 minutes
18M - 3 minutes
15M - 3 minutes
12M - 4 minutes
9M - 4 minutes

There is no right or wrong, and different people do different things. It becomes far more regimented at the Tech2 and Tech3 levels, but at the Tech1 level, you will get away with pretty much anything. Howard has put the bag up now. we'll wait until the clock hits three minutes at 21M and then move through the intermediate stops. We'll actually move a little faster so we are moving for 30 seconds and stablisiing for thirty seconds. Up we go to 6 metres.

Shaping the Decompression Curve - Shallow Stops.

Well, here we are at 6 metres. We had 30 minutes of decompression to do, 15 of which we did in the intermediate stops, and 15 of which we need to do here. We have a few options here. We could just do 15 minutes at 6 and then ascend over 5 minutes. If the surface conditions did not allow this we could do 18 mins and then a 2 minute ascent. Team foxturd take the best of both world, and would do the 15 minutes at 6 and then attempt a 5 minute ascent. But we're in no rush to get to the surface.

That was easy, wasn't it.

The simple example

45 metres. 30 minutes.

We thumb the dive and leave the bottom. We need to get to 80% of the ATAS. Let's see, thats 5.5 X 2 taken away from 45. That's means 34 metres. Let's call it 33.

We go up to 33 at 9 metres per minute. It takes just over a minute. We slow down to 23 metres per minute and it takes us another 4 minutes to get to 21 Metres. We started at 45 metres so its the 1: 1 ratio. We did 30 mins so we have 30 mins deco to do, 15 in the intermediate stops and 15 in the shallows.

We then switch gas and bag up.

15 minutes is divisible by 5, which makes the deco easy...

21M - 3 minutes
18 M - 3 Minutes
15M - 3 Minutes
12 - 3 Minutes
9M - 3 Minutes

Now we are at 6 metres. We have 15 minutes to do so we do them and then ascend as slowly as possible


The complicated example.

Here we are on the Salsette. We have been swimming around and over things so the average depth is actually 42 metres. We have been on the bottom for 28 minutes. Gareth hits minimum gas, so we thumb the dive. We leave the bottom immediately on thumbing the dive.

Up we go at 9 metres per minute. 80% of the ATAS from 42 metres is 5.2 *2 = 10.4 taken away from 42 = 11 metres, so lets call it 31 metres. Actually, we call it 30. It takes us a minute and a bit to get there.

At 30 we slow down to 3 metres per minute. It takes us a further 3 minutes to get to 21 Metres. During which time I'll have probably worked out the deco.

Now we gas switch and put a bag up. We do 3 minutes at 21M.

We did 42 metres for 28 minutes. thats 3 metres less than 45 so take off 5 minutes. We have 23 minutes deco to do. Sod that, let's do 24

Half of 24 is 12, divided by 5 is not possible so let's do the following

21 M = 3 Minutes
18 Metres = 2 Minutes
15 Metres = 2 Minutes
12 Metres = 2 Minutes
9 Metres = 3 Minutes

Up we go through the intermediate stops.

Now we are at 6 metres. We have 12 minutes to do

Let's keep things simple. 12 minutes at 6 and then ascend as slowly as possible.

Dive Over.

Now wasn't that painless?

Comparisons with Dive Models

The nearest model to ratio deco for the sake of comparison is gradient factors of 30/85

Taking our two dives,

the 45 metre /30 min dive would give us a runtime of about 66 mins (with a 3 minute ascent from 6m), as compared to a runtime of 63 mins from decoplanner.
the 42 metre / 28 min dive would give us a runtime of about 59 mins (with a 3 minute ascent from 6M), as compared to a runtime of 53 mins from decoplanner.

It will be closer or further away depending on the depths and times. Ratio deco is not perfect, it suits some dives better than others.

Summary

DIR is not about a perfect configuration, or a perfect set of standards. It's about providing a kit configuration and set of standards that can be applied everywhere. It may be a good fit in some situations, and a poorer fit in others, but there is so much advantage in having the standard that DIR divers who think through all the standards just have to accept this.

Ratio Deco, like everything else in DIR, does not provide the perfect option for all scenarios. However, it does provide an option that fits all scenarios to a greater or lesser degree. Learning where these degrees are is all part of the education process. If we dived to 54 metres, I probably wouldn't be happy with 1:1, but would start padding it out.

Whilst on the subject of padding, the question may arise where one person in the team wants to do more deco. It doesn't matter why. The most conservative person always wins. Of someone wants to extend the stops, that's what we do, no discussion, no arguments.

One interesting point is that if you always round up the deco to the next ten minutes, it all becomes ridiculously easy. Lets say we have 30 minutes deco to do. That's 15 in the intermediate stops and 15 in the shallows. I get to 18 metres and signal 3. If we follow the rule of always rounding up the deco to the next ten minutes then the team know from that one signal exactly how much deco I am planning on doing at each stop, and the total amount of deco we have to do. However, that is making the assumption that you don't mind doing a few extra minutes deco.

We do not really have to worry about carrying enough deco gas becuase using this form of ratio deo and using twin 12s means we will not be able to get into the position of not having enough deco gas unless we lose our AL80 deco bottle. If that happens, Ratio Deco also allows for a lost deco gas. We can just double the stops and deco out on the back gas. At the Tech1 level, it just works in terms of gas logistics.

Now, just on a closing note, for the love of God don't go out and do this without training in all the other elements I have mentioned. However, I hope it has been useful information and an interesting read

Dive safe everyone

Garf.

DIR Minimum Gas - Explained

Minimum Gas
The DIR concept of “minimum gas” is the unbreakable rule by which we plan our dives. Minimum gas represents the minimum amount of gas carried by each diver that will allow the diver to get themselves, and another diver, to the next available gas source. For a short shallow dive, this might mean a direct ascent to the surface. For a longer dive with mandatory decompression stops, this might mean the ascent to a depth where it becomes appropriate to switch to another gas. Minimum gas is an absolute. It is never violated during the bottom portion of the dive, and once minimum gas is reached, the only option is to call the dive and ascend immediately.

Gas Rules
This is how we plan our gas to be used. Let’s say our minimum gas is 70 Bar in our twinset, and we start the dive with 220 bar. That means we have 150 bar of usable gas. With that 150 bar, we then apply a gas rule. That rule might be thirds (when the dive MUST return to a starting point), halves (when it would be useful for the diver to return to the start point but not essential) or all useable gas (where the diver can just ascend from wherever they are and be picked up). The “All useable gas” rule is often applied in UK waters where the boat can just come and get us, but we might apply halves if the skipper wants us to return to a shotline. The beauty of the gas rules is that if we get back to our starting point early, and ahead of minimum gas, we can just recalculate our halves, or thirds, and go off again.

Calculating Minimum Gas

The fundamantal principle. At all times, a DIR diver enough gas to get themselves, and a team mate, to the next available gas source.

OK, so in order to know how much gas we have available for the dive, and in order to know our safety factor, we have to be able to calculate minimum gas. I’m going to run through two examples, a thirty metre dive where we can ascend directly to the surface, and a 45 metre dive, where we have to ascend to 21M to do a gas switch

30 Metre Dive

To calculate min deco, we make several assumptions.

• Firstly, we assume an ascent rate of 9M per minute to 50% of the depth, then 3 Metres per minute after that.
• Secondly, we assume a SAC rate of 30 Litres per minute for both divers. This might seem high to some people. But, in an incident, SAC rate can hit 100. Even if it then settles down, it’s going to average out significantly higher than your normal rate
• We assume one minute at the bottom sorting out whatever has gone wrong and getting moving

So, here we are at thirty metres, and all hell breaks loose so two divers have to ascend directly to the surface on one diver’s backgas.

50% of 30m = 15 metres
So, from the bottom

1 Minute resolving Issue
2 Minutes to get from 30M to 15M (plan on 9m/min but most people achieve around 7m/min)
1 Minute to get from 15M to 12M
1 Minute to get from 12M to 9M
1 Minute to get from 9M to 6M
1 Minute to get from 6M to 3M
1 Minute to get from 3M to the surface

This means a 8 minute ascent time.

Now we need to know the average depth. For the dive above, I would call the average depth 10 Metres or 2 Bar

8 minutes of Gas for 2 divers = 16 minutes of Gas required
Depth consumption Rate = 2 Bar X 30 Litres = 60 Litres Per minute

16 X 60 = 960 Litres of Gas Required

Therefore minimum gas for this dive would be 960 litres of gas, or 40 bar in a set of twin 12 litre cylinders.

So, on a 30 metre dive, with both divers using twin 12s, we know we need to leave the bottom before we hit 40 bar to ensure that if there is a total loss of gas for one diver, we can safely and slowly ascend to the surface. This might be far more conservative than other measures due to the slow ascent rate, but it is very comforting to know we can ascend at this rate and still know we have enough gas.

If we have a 220 bar fill in the twinset, and are going to be picked up by the boat, this gives us 160 bar to use during the dive which is nice.

Some people might find the maths a little baffling, but others might just see it immediately. Once you run a few of them through your head you can do it simply enough. We would do this before we hit the water if it was a known depth, or at the bottom of the shotline if it was different than expected.

Now, these figures are always the same, so you could work out the min gas required for each depth, or write them on a slate. However, this defeats the true strength of the calculation, and it is strongly encouraged that DIR divers learn to do this in their heads. Here’s the reason. Let’s say you reach the seabed, and the depth is shallower or deeper than you planned, you can just recalculate minimum gas on the spot and make the most of the gas you have with you without risking safety. That last factor is the real winner for me, and the calculation is simple enough after a while.

Let’s take the calculation a little deeper, shall we say 45 metres?


45 Metre Dive

On this dive, we are at 45M and we are carrying a stage of 50%. Remember that Minimum gas is supposed to get you and another dive to the next available gas source, which in this case is 21M where we would switch to the 50%.

We use the same SAC of 30 Litres Per minute.

80% of the ATAs (or 75% depth) in this case is 34 metres, but for simplicity we deal in multiples of 3 metres, so we will call it 33 metres.

This, then is the ascent profile

1 minute at 45 metres resolving issue
2 minutes to get from 45 to 33 (its more than 9 metres so has to be 2 minutes travel)(upto 80% = 9mtr/min)
1 minute to get from 33 to 27 (80% to 21m = 6mtr/min)
1 minute to get from 27 to 21
1 minute to allow for gas switch

This gives us an 6 minute ascent to the gas switch

Now we need to know the average depth. For the dive above, I would call the average depth 33 Metres or 4.3 Bar.

The calculation, then…

6 minutes of Gas for 2 divers = 12 minutes of Gas required
Depth consumption Rate = 4.3 Bar X 30 Litres = 129 Litres Per minute

12 X 129 = 1548 Litres of Gas Required.

In a set of twin 12s this would equate to 65 bar. Again, we will round this up to be 70 bar. Assuming a 220 bar fill, and again using the gas rule of all available gas, this means we have 150 bar of gas to play with before we have to leave the bottom.

So that’s minimum gas a la DIR.

Remember that you “could” always get up a lot faster than this, but why not plan for a nice controlled, slow ascent, rather than planning for a race up to the surface.

In addition, the numbers here are exact, but in the case of a different bottom depth, it would be advisable to use easier numbers e.g. 4.5 instead of 4.3 (working this through min gas would still be 70bar rounded up).

Finally, as the depths increase, the time spent at 1.5x your normal SAC during the ascent is not realistic and also becomes penalising and so those DIR divers doing Tech 2+ depths use a different average SAC rate than 1.5x

Finally, just a reminder of the Golden Rule

At all times during a dive, we carry enough gas to get ourselves, and a buddy or team mate, to the next available gas source. This rule is never violated.

Hope this has been useful to someone

Garf

(updated due to standards change by Wilbo)