Article: But I cant be bent, my computer says I did everything right
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Using a PDC is not enough. Understanding what the PDC does is not enough. Understanding DCS and how to prevent it, understanding the mechanisms of gas exchange and its effects and knowing how to deal with them is not enough.
Electronics and knowledge in whatever amounts cannot guarantee 100% prevention. Only refraining from diving can.
Electronics and knowledge in whatever amounts cannot guarantee 100% prevention. Only refraining from diving can.
Very good article!
Given the same dive profile, a dive computer will produce the same results - day after day. Our body will not!
Given the same dive profile, a dive computer will produce the same results - day after day. Our body will not!
3william56
Registered
"I have witnessed divers pulling out batteries, hanging computers in the water “to decompress,” and even leaving their PDC on the boat for a dive to “cool off.” None of this is a good idea. Seriously."
Until a couple of months ago, I would have hoped divers were smarter than this. But not any more.
Not only do people think that diving within the limit of a computer is completely safe, far too many assume that the comp has a massive safety margin built in, so it's OK to push the limits, or even break them.
In a recent series of dives on the President Coolidge in Vanuatu (to 40-69m on air, with ~50mins deco times) I witnessed a group of divers coming to the surface early after each dive, then throwing their comps back in the water on fishing line to "finish" the stop. When asked, they said "computers are too conservative" and they were bored (the deco stop was in a stunning coral garden with rainbow mantis shrimp, clownfish eggs spawning and the occasional dugong flyby - bored!!!). After a couple of days, one diver's comp went into violation anyway, and we saw him flipping the battery to glitch it out of violation. When it didn't work, he bullied a local dive guide to borrow a new comp for their last dive. To cap it off, one woman in the group wondered why she was getting headaches and bleeding from the nose and ears. This was on a full penetration wreck dive where there had been a fatality in the last few months.
After my wife (>400 dives DM) and I tried to talk to them about how dangerous this was to no avail, all we could do was insist that they dive well away from us. Not willing to risk ourselves in a rescue situation to save idiots.
Until a couple of months ago, I would have hoped divers were smarter than this. But not any more.
Not only do people think that diving within the limit of a computer is completely safe, far too many assume that the comp has a massive safety margin built in, so it's OK to push the limits, or even break them.
In a recent series of dives on the President Coolidge in Vanuatu (to 40-69m on air, with ~50mins deco times) I witnessed a group of divers coming to the surface early after each dive, then throwing their comps back in the water on fishing line to "finish" the stop. When asked, they said "computers are too conservative" and they were bored (the deco stop was in a stunning coral garden with rainbow mantis shrimp, clownfish eggs spawning and the occasional dugong flyby - bored!!!). After a couple of days, one diver's comp went into violation anyway, and we saw him flipping the battery to glitch it out of violation. When it didn't work, he bullied a local dive guide to borrow a new comp for their last dive. To cap it off, one woman in the group wondered why she was getting headaches and bleeding from the nose and ears. This was on a full penetration wreck dive where there had been a fatality in the last few months.
After my wife (>400 dives DM) and I tried to talk to them about how dangerous this was to no avail, all we could do was insist that they dive well away from us. Not willing to risk ourselves in a rescue situation to save idiots.
lemke
Contributor
You can understand the physiology of decompression all you want... until you are intimately familiar with the physiology of decompression of YOUR body, your DC is merely giving you a best guess.
reefrat
Contributor
I agree with every comment and sentiment in the article above- thanks to Steve for writing it.
One thing that I regard as important in attempting to prevent DCS is a "good" profile!
Most divers seem to think that it does not matter what they do as long as the little NDL number stays above zero all will be OK! Meanwhile they blissfully yo-yo up and down in depth, dive a squarer or reverse profile and head down again for that one last look at a interesting critter before zooming up to the "safety stop"! Of course when they are groaning in pain on the deck they will complain that they did not go into deco so it was an undeserved hit!
Dive computers are critically important but can only be effective in combination with a sound understanding of what constitutes a safe profile, and I see a LOT of ignorance out there on what that is.
I will not own a computer that does not show maximum depth and elapsed time. In the first 1/3 of any dive I am watching max depth closely until I mentally establish that I have reached it and the rest of my dive will be progressively shallower. For the remainder of the dive every time I look at my computer (every few minutes) I am creating a mental image of what my profile looks like with a a progressive ascending curve and at least half of the dive occurring at 1/2 or less than the maximum depth. It's not difficult to do, it's just force of habit after a while.
Of course some dives require a square profile but I manage that with ultra conservatism.
Maybe one day I will get bent, but not if I can help it!
One thing that I regard as important in attempting to prevent DCS is a "good" profile!
Most divers seem to think that it does not matter what they do as long as the little NDL number stays above zero all will be OK! Meanwhile they blissfully yo-yo up and down in depth, dive a squarer or reverse profile and head down again for that one last look at a interesting critter before zooming up to the "safety stop"! Of course when they are groaning in pain on the deck they will complain that they did not go into deco so it was an undeserved hit!
Dive computers are critically important but can only be effective in combination with a sound understanding of what constitutes a safe profile, and I see a LOT of ignorance out there on what that is.
I will not own a computer that does not show maximum depth and elapsed time. In the first 1/3 of any dive I am watching max depth closely until I mentally establish that I have reached it and the rest of my dive will be progressively shallower. For the remainder of the dive every time I look at my computer (every few minutes) I am creating a mental image of what my profile looks like with a a progressive ascending curve and at least half of the dive occurring at 1/2 or less than the maximum depth. It's not difficult to do, it's just force of habit after a while.
Of course some dives require a square profile but I manage that with ultra conservatism.
Maybe one day I will get bent, but not if I can help it!
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Great stuff here Steve - thanks for putting it together and sharing! It is so important that every diver understand that we plan and monitor dives to reduce risk not eliminate it. Trying to second guess your computer is just asking for trouble.
Always a fan of reading your articles Steve!
I did a dive on the Forest City in Tobermory. There were 6 of us in the water, all dove essentially identical profiles, one of us ended up in the chamber.....no violations of any kind on the computer that he was using, nor on any of ours.
It happens. You can do everything right and still end up having everything go pear shaped.
I did a dive on the Forest City in Tobermory. There were 6 of us in the water, all dove essentially identical profiles, one of us ended up in the chamber.....no violations of any kind on the computer that he was using, nor on any of ours.
It happens. You can do everything right and still end up having everything go pear shaped.
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