DECO the Dark site in recreational Diving
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Mustard Dave
Contributor
I was involved in a bit of an incident a couple of weeks ago. It was due to unplanned deco as a result of a diver not monitoring her computer, but it illustrates the dangers that can arise if you don't know what you're doing when it comes to deco.
I was in the Mediterranean in warm, clear blue seas. I was diving with a group of seven from my club with two guides (both PADI instructors) from a dive centre we have used for the last five years. The dive centre don't try to nanny us and generally let us do our own thing, which is one of the things we like about them. Everybody on the trip is a seasoned UK diver and five of us have dived here several times. The site is a shore dive with two wrecks sunk as artificial reefs, at a depth of 25-37 metres. The entry point is a shallow pool - about 6 metres at its deepest point. The pool opens up and drops steeply to the maximum depth.
We had a pleasant dive around one of the wrecks and headed back to the entry/exit point. I had ten minutes of deco at 6 metres by the time we got back to the pool. At the entry to the pool, there is a bit of a lip formed by the rocks at the entrance at a depth of 5 metres, so I couldn't enter until I'd cleared my deco. Once clear, I ascended and entered the pool. There is a lot of life in there and I had quite a bit of gas, so my buddy and I had a bimble around for a while. As we moved closer to the exit, I spotted one of our group. She was on the bottom, clinging to a rock, with her buddy on oner side and one of the guides on the other. The other guide was hovering nearby. At first I thought they had seen something and were watching it, but as I got nearer, I saw she was on her buddy's octopus. I guessed what was going on so I swam over. I told the guide I had 60 bar and she beckoned me over. I had a hog-looped long hose which I donated. When my gas was depleted, she signalled me to get out and called my buddy over to donate gas.
When I got out of the water, I saw her buddy (who is her partner). I asked him what had happened and he told me he had 15 minutes deco. He said he had noticed she was deeper than him on the way back and was trying to tell her to come up, but she didn't respond. A few minutes later, she was walking over to us, looking somewhat relieved. She told me she had never been into deco before and crapped herself when she saw her computer. She said when she was on her partner's octopus, she just stared at a rock and tried to zone out to make the time pass.
The guide said she was relived to see me, as the victim's buddy was getting low on gas. As I was the only one diving with a long hose, it made it so much easier to donate gas. She wanted to avoid donating her own - that way she could make sure she could stay in the water and keep an eye on things.
I understand the two guides had a bit of a telling off when the dive centre owner heard, which I think is unfair. We were all experienced divers so they left us to get on with things; he has dived with us on many occasions and he has always done the same - nobody has ever checked our computers.
I have no idea how long the victim has been diving, but I know it is longer than I have. I was puzzled how she got herself into that situation, considering she has been on several dives in similar depths. She had a Suunto computer, which I know beeps when it hits deco. Another question is what was she monitoring on her ascent? How did she not spot the computer was in deco then? I suspect she usually follows her partner.
Hopefully she has learned something from this. What others can learn from it is deco + little gas = squeeky bum time, and that gas management is one of the most important considerations when deco diving.
I mostly agree with what you are saying. A small amount of deco is no big deal, but it is not without risks. With the PADI system (I'm not picking on PADI - it's just that they and BSAC are the only agencies I am familiar with at 'recreational' level) a diver theoretically can go straight from novice to 'Deep Diver' in 12 open water dives (4 for OW, 5 for AOW and 3 for deep). For a diver with such little experience, going into deco is not wise, as you don't know how they would react to an emergency, and we all know the instinct is often bolt for the surface.
With BSAC divers trained in a club situation, the training is generally at a slower pace; when a BSAC diver gains their 'Sport Diver' certification, they are usually reasonably experienced club divers.
The part of your post that slightly puzzles me is the last sentence - it appears you are suggesting bailout is an option. I would have thought all agencies would teach a redundant gas source is essential for deco diving. I have done dives with a small amount of deco on a single, and will probably do so again, but this is generally in warm blue water with plenty of divers around to donate gas; this is my choice though - I'd never advocate such practices, particularly if I was representing a diver training agency.
I think you can have simple deco diving and simple deco diving - 5 minutes deco versus 90 minutes is a big difference. IANTD limited my deco to 15 minutes on my advanced nitrox certificate, which was my first deco certification. With cave diving, again there are a number of factors. How deep is the cave? How much room is there? Do you go beyond the zone where light penetrates? How long is it to the exit? etc.
The reason I think many divers push NDLs is it is so easy to hit them. On PADI tables, 8 minutes at not a long time for a dive, but that's all you get at 40 metres. Many will want to stay longer - I know I did. How you then go about doing it is the important bit though.
I was in the Mediterranean in warm, clear blue seas. I was diving with a group of seven from my club with two guides (both PADI instructors) from a dive centre we have used for the last five years. The dive centre don't try to nanny us and generally let us do our own thing, which is one of the things we like about them. Everybody on the trip is a seasoned UK diver and five of us have dived here several times. The site is a shore dive with two wrecks sunk as artificial reefs, at a depth of 25-37 metres. The entry point is a shallow pool - about 6 metres at its deepest point. The pool opens up and drops steeply to the maximum depth.
We had a pleasant dive around one of the wrecks and headed back to the entry/exit point. I had ten minutes of deco at 6 metres by the time we got back to the pool. At the entry to the pool, there is a bit of a lip formed by the rocks at the entrance at a depth of 5 metres, so I couldn't enter until I'd cleared my deco. Once clear, I ascended and entered the pool. There is a lot of life in there and I had quite a bit of gas, so my buddy and I had a bimble around for a while. As we moved closer to the exit, I spotted one of our group. She was on the bottom, clinging to a rock, with her buddy on oner side and one of the guides on the other. The other guide was hovering nearby. At first I thought they had seen something and were watching it, but as I got nearer, I saw she was on her buddy's octopus. I guessed what was going on so I swam over. I told the guide I had 60 bar and she beckoned me over. I had a hog-looped long hose which I donated. When my gas was depleted, she signalled me to get out and called my buddy over to donate gas.
When I got out of the water, I saw her buddy (who is her partner). I asked him what had happened and he told me he had 15 minutes deco. He said he had noticed she was deeper than him on the way back and was trying to tell her to come up, but she didn't respond. A few minutes later, she was walking over to us, looking somewhat relieved. She told me she had never been into deco before and crapped herself when she saw her computer. She said when she was on her partner's octopus, she just stared at a rock and tried to zone out to make the time pass.
The guide said she was relived to see me, as the victim's buddy was getting low on gas. As I was the only one diving with a long hose, it made it so much easier to donate gas. She wanted to avoid donating her own - that way she could make sure she could stay in the water and keep an eye on things.
I understand the two guides had a bit of a telling off when the dive centre owner heard, which I think is unfair. We were all experienced divers so they left us to get on with things; he has dived with us on many occasions and he has always done the same - nobody has ever checked our computers.
I have no idea how long the victim has been diving, but I know it is longer than I have. I was puzzled how she got herself into that situation, considering she has been on several dives in similar depths. She had a Suunto computer, which I know beeps when it hits deco. Another question is what was she monitoring on her ascent? How did she not spot the computer was in deco then? I suspect she usually follows her partner.
Hopefully she has learned something from this. What others can learn from it is deco + little gas = squeeky bum time, and that gas management is one of the most important considerations when deco diving.
I mostly agree with what you are saying. A small amount of deco is no big deal, but it is not without risks. With the PADI system (I'm not picking on PADI - it's just that they and BSAC are the only agencies I am familiar with at 'recreational' level) a diver theoretically can go straight from novice to 'Deep Diver' in 12 open water dives (4 for OW, 5 for AOW and 3 for deep). For a diver with such little experience, going into deco is not wise, as you don't know how they would react to an emergency, and we all know the instinct is often bolt for the surface.
With BSAC divers trained in a club situation, the training is generally at a slower pace; when a BSAC diver gains their 'Sport Diver' certification, they are usually reasonably experienced club divers.
The part of your post that slightly puzzles me is the last sentence - it appears you are suggesting bailout is an option. I would have thought all agencies would teach a redundant gas source is essential for deco diving. I have done dives with a small amount of deco on a single, and will probably do so again, but this is generally in warm blue water with plenty of divers around to donate gas; this is my choice though - I'd never advocate such practices, particularly if I was representing a diver training agency.
I think you can have simple deco diving and simple deco diving - 5 minutes deco versus 90 minutes is a big difference. IANTD limited my deco to 15 minutes on my advanced nitrox certificate, which was my first deco certification. With cave diving, again there are a number of factors. How deep is the cave? How much room is there? Do you go beyond the zone where light penetrates? How long is it to the exit? etc.
The reason I think many divers push NDLs is it is so easy to hit them. On PADI tables, 8 minutes at not a long time for a dive, but that's all you get at 40 metres. Many will want to stay longer - I know I did. How you then go about doing it is the important bit though.
Dr. Lecter
Contributor
That locking method is simply brilliant...wish my can light had it instead of those stupid metal latches.
If you don't do deco diving, you've never seen what your computer looks like in deco mode. Suunto computers simply start to show your accumulated deco obligation where your NDL time used to be listed. There's no flashing red lights, nothing that states "YOU ARE NOW IN DECO" or anything. Assuming such folks are paying any attention at all, they still might not notice... until they get to their safety stop and realize that instead of saying "STOP: 3" the countdown timer says "STOP: 19" or something.
Most likely, she silent her alarms, I see this behavior common with very experienced divers, don't understand why silent an extra safety, even if they are super dupper divers, I guees it is their perspective of thier own confort zone.
lv2dive
Formerly known as KatePNAtl
There are a lot of experienced divers who don't even have alarms to silence! How in the world do they make it to the surface safely?!????
Dr. Lecter
Contributor
ing Shearwaters, how do they work?!
PfcAJ
Contributor
bamafan
Contributor
From my experience most recreational computers do not handle deco really well. I use to dive an Oceanic Versa Pro when I first started diving. I then started cave diving and trimix and decided I wanted a computer that could handle mix and O2. I bought a Predator when they came out. I used my Oceanic as a backup for a while. Running 30/70 the Predator would be showing a minute or two of deco and the Oceanic would have 5 -10 minutes left. Now when the Oceanic went into deco it would start giving unrealistic times. I would have 20 -30 minutes on the Predator and 2 - 3 hours on the Oceanic. I bought a Petrel when they came out and now they clear within a minute or two of each other.
oldschoolto
Contributor
I've been lurking this thread... I do have a few concerns about the original posters abilities... The biggest red light for me , Is his concern about the simple loss of a mask...
First off, Every dive is a deco dive.... I learned to dive by reading " The science of skin and scuba " when I was 12 years old... I was doing solo wreck dives at 15 to 175' on steel 72's doubles with a 40 pony bottle... Using the navy tables... because thats all we had.. I would hang a steel 72 at 15' for the last of any deco that was needed... I didn't have a computer because they were not invented yet.. Didn't have a pressure gauge because the double hose Aqua-master has no port for one... I knew the tables and knew what was safe and what was not... Anything is doable if a person takes the time to learn and goes slow...
But at 25 dives.... The first thing he should do is get a spare mask for his BC pocket and take baby steps... You should be fearless of problems and have a plan to deal with every possible thing that could go wrong.. He needs more training.. On his own, With a mentor or a paid class... Hope he listens to all the good advice he was given...
Jim...
First off, Every dive is a deco dive.... I learned to dive by reading " The science of skin and scuba " when I was 12 years old... I was doing solo wreck dives at 15 to 175' on steel 72's doubles with a 40 pony bottle... Using the navy tables... because thats all we had.. I would hang a steel 72 at 15' for the last of any deco that was needed... I didn't have a computer because they were not invented yet.. Didn't have a pressure gauge because the double hose Aqua-master has no port for one... I knew the tables and knew what was safe and what was not... Anything is doable if a person takes the time to learn and goes slow...
But at 25 dives.... The first thing he should do is get a spare mask for his BC pocket and take baby steps... You should be fearless of problems and have a plan to deal with every possible thing that could go wrong.. He needs more training.. On his own, With a mentor or a paid class... Hope he listens to all the good advice he was given...
Jim...
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