Short story, four diving instructors took themselves on a dive to 40m. Although young, they were experienced. At depth they found two tanks were empty, and the other two didn't have enough in them to get the four back to the surface. They suffered varying levels of the bends, leaving one paralysed.
They now know that what happened was "a disparity between what was planned in terms of breathing rates and what actually happened on the dive". It was unpredictable.
Now, I haven't done much diving in recent years, and am only qualified to PADI Advanced Open status, (that's about third level qualification), but I call bullshit. There is no way on this planet that four instructor-level divers should get themselves into such a mess.
I know there are a few divers in this forum, what are your views?
Welcome to Britain, if you don't like the weather, just wait a minute, some more will be along soon.
I haven't dived in several years now, but when I started I had a tendency to breath too fast, and usually was the first person back to the boat. But I always kept an eye on my pressure gauge, so I always had enough left over.
Something is screwy if the first sign that he was out of air was the tightness of the mouthpiece. Weren't they looking at the gauges the whole time?
I'm neither an optimist nor a pessimist, I'm pragmatic. I see another friggin' glass to wash.
I obtained my PADI Open Water Dive certification years and years ago in college. Even then when you were planning dives, (without computers but charts) you allowed extra time for nervousness, excited, etc., and you were constantly told to check your gauges. I do remember being taught that you can ascend slowly a foot per second and we would practice this from a depth of 40 ft. The theory was you could exhale all the way up from 40 ft ascending a foot per second. It is a very slow ascent.
I also find it hard to believe that these divers made that mistake especially since they were instructors.
Right you are Mank. I've been certified since the early 60's and have a buncha dives - under ice even... You might say I 'been there done that'. The point of this story is this:
"At depth they found two tanks were empty, and the other two didn't have enough in them to get the four back to the surface"
And like Malcolm, I call bullshit too. I've been at 60' and ran completely out of air - back then we DIDN'T have gauges other than the ONE gauge that you used on the surface to see if your tank had pressure and how much. We had 'horse collars' (no BC's) and used double hose single stage regulators (remember them?). No one had ever heard of an 'octopus' and so we had NO GAUGES while in the water. And one other thing, remember the 'J' valve? Had a little ring on the end of a rod against the tank (so you could reach around and find it) and at +/- 300 psi your tank would 'run dry' - so you pulled the valve and now you had that 300 psi to get you the surface comfortably.
Well on that particular 60' dive I 'ran out of air'. Yup. Dead stoppage. So being the experienced super diver I am, I reached around to pull the valve and get my reserve air. The DAMN THING had snagged on something and I was REALLY out of air! No reserve! Ok, 60' with no air.... did I die? By the way, I was diving alone...
This is where the bullshit in the story comes in - you DON'T NEED air in your tank if you're ascending - you can exhale all the way to the surface as the air in the tank expands due to lessening of pressure, just like Mank said. It's not a 'theory' Mank, it's Boyle's law of expanding gas in action...
You brought back some memories, the double hose single stage regulators, and the J valve, which I completely forgot about. I do know that you can exhale all the way up from 40 ft and did practice that while obtaining certification.
There is a training tower at the New London Naval Base. You open the door at the base and are in 100 ft. of water with no life jacket. You blow a bubble into a cloth canopy and exhale all the way to the top. My brother did it often enough for enjoyment that he was told to not do it again. There are divers in the tower at various depths with Oxygen if you get in trouble
Inside every old person is a young one wondering, What the Hell Happened!
That detail was noticed. I noticed it because I'm a certified 'mixed gas, technical diver' and I use Nitrox I (32%) or Nitrox II (36%) on every dive that I can get it. The limit for Nitrox I is 130', Nitrox II is even less.
But you know that lousy head-achy feeling you get after that first dive of the day? It doesn't happen if you're using NITROX! Really. AND your bottom time is extended by about a third. Again, really.
Here's some factoids: Over 130' for Nitrox I it becomes more and more poisonous to the body so a depth (pressure) limit of 3+ atmospheres is required for safe use. Keep in mind that is the FIRST DIVE OF THE DAY! After that, you change to air and keep a close eye on your decompression tables, or if you're rich, your fancy-assed dive computer. For me, l don't fancy the idea of my safety depending on some damn waterproof smartphone, thank you. A good dive plan will save your ass every time.
Do you know why all single scuba dive cylinders are 80 or 82 cubic feet capacity? It's because diving with that amount of air at 3200 psi in an 82 cu tank of AIR, you CANNOT get down far enough and stay long enough to REQUIRE any decompression stops at all!
Now that's the FIRST dive - you can possibly get to 40m but your time at that depth is less than 5 minutes - then you run out of air and have to ascend - breathing all the way to the surface, incidentally... You can go UP, but not DOWN. Boyle's law won't let you. And NO DECOMPRESSION required. Again, first dive of the day...
Now when you have double 82's or even 100's you better have your shit together and PLAN your dive in detail. That's why I call bullshit on 4 'professional' divers fucking up so badly they damn near kill themselves.
On repetitive dives (same day), you will need decompression but how many stops and the depth of each depends on mixture (air or nitrox, or an exotic [helium]), how long between dives, depth of the second and subsequent dives, and other stuff, but if you're a certified 'professional' that shouldn't be a problem, should it?
- L -
Last Edit: Aug 6, 2018 14:55:10 GMT -5 by mollypop