Deep bounce dive in Cozumel leads to missing diver

[stevep4444]

The 200-250ft bounce dives on a single al80 happen more frequently than I would have thought. It is not something that interests me at all but a little research through past threads on this board and knowing a few who do them lead me to believe it is not as rare as I expected. If I was in the water a lot I could see how going on progressively deeper dives and going deeper than 200 ft on a single 80 could happen over time. The reality is I simply do not dive enough to even have it cross my mind.

 

[TSandM]

You know, I've gotten my technical training, and I've done some technical diving . . . I can understand going deep for a specific purpose, like visiting a historic wreck. But to go deep for the sake of doing it? I've been down there . . . there's nothing different about 170 feet compared with 30, except it's darker and there is less marine life. And it's an awful long way to the surface, if anything goes wrong. I have the training and I have the equipment and access to the gas . . . and most of my dives are in the top 100 feet. Heck, most of them are in the top 60, and some of the most fun ones are shallower than that. With the exception of the Carthaginian, our max depth for this trip to Maui was 30 feet . . . and we saw a manta, a pod of dolphins, innumerable turtles, a seahorse, frogfish and TONS of other fascinating creatures. I don't understand the allure of depth for its own sake, when you can have just as much fun much more safely when you are closer to the great air tank in the sky.

 

[Gdog]

I have to go with Dirty-Dog here..calculate rock bottom gas needed for this dive, and you see that an AL80 is roulette with your life. Of course there may be enough gas to do the bounce. As long as everything works flawlessly. Unfortunately, that isnt reality. Mr Murphy likes to meddle with reality.

 

[AfterDark]

You know, I've gotten my technical training, and I've done some technical diving . . . I can understand going deep for a specific purpose, like visiting a historic wreck. But to go deep for the sake of doing it? I've been down there . . . there's nothing different about 170 feet compared with 30, except it's darker and there is less marine life. And it's an awful long way to the surface, if anything goes wrong. I have the training and I have the equipment and access to the gas . . . and most of my dives are in the top 100 feet. Heck, most of them are in the top 60, and some of the most fun ones are shallower than that. With the exception of the Carthaginian, our max depth for this trip to Maui was 30 feet . . . and we saw a manta, a pod of dolphins, innumerable turtles, a seahorse, frogfish and TONS of other fascinating creatures. I don't understand the allure of depth for its own sake, when you can have just as much fun much more safely when you are closer to the great air tank in the sky.

From the Advanced site : http://www.scubaboard.com/forums/advanced-scuba-discussions/455535-200-air-5-min-bottom-time-6.html

IMO 200'+ isn't what I call "safe" depths unless you can breathe water. More than a few experienced, well trained, well equipped divers have not come back from those depths because of small things going wrong that may not have been fatal at shallower depths. Unless there is a reason to dive that deep why do it on any mix? I understand it some; I was a new diver and fascinated with what might be at deeper depths...............More fodder for A&I.

 

[lamont]

Then you have to wonder about a person's risk of debilitating nitrogen narcosis. Like many things, that could vary among people. Looking back at the Scuba Mau event, unverified recollection is that the plan was to 250' or possibly deeper. At least two of the three people on that dive lived in Cozumel so they had the chance to make frequent deep dives. Were they comfortable with the effects of air at that depth that the risk was relatively low or did others factors come into play to make it a lethal dive?

At that depth, breathing air, the gas density is 11g/L. The allowable max is generally quoted as 8g/L (equivalent to air at 50m/170ft -- which I still wouldn't recommend) while Dave Shaw's fatal CO2 hit took place with a gas density of around 10.1g/L (although Dave was on CCR and not OC, so WoB may have been inherently high, but we don't know how well the OC regs were tuned in this case). At that kind of density the gas you are breathing is becoming more syrupy and your ventilation is becoming impaired and you will suffer CO2 hits much more easily. A little exertion, a crappy breathing reg, a little bit of panic and elevated heartbeat and breathing, a small problem with gear like a fin coming loose or whatever can cause a spiral into a full blown CO2 hit - most likely resulting in the diver passing out due to the narcotic effects of CO2... This is why diving at those depth on air is like roulette. You may be able to cheat it any number of times before you have the dive where you trigger a CO2 spiral and it gets you.

One of the other effects of helium is to reduce the density and viscosity of the breathing gas, produce more laminar flow and reduce the work of breathing. Heliox mixtures are also used in emergency medicine for this purpose for patients with certain kinds of airway issues.

We've had multiple fatalities up here due to 200 foot bounce dives on Al80s with air. We've also had some OOA fatalities in divers with Al80s just going to 100 feet and getting narc'd and running out of gas. It seems like Coz is starting a new trend of bounce dive fatalities...

 

[ajduplessis]

Self-administration of chlorine to the gene pool.

 

[Dive Bug Bit Me]

I think it's more not realising what you don't know.

I've had a recreational instructor with a couple of thousand dives proudly tell me his maximum depth was 200ft and that he limited it there because of PPO2. 'twas a single 80 tank.

I explained that I've been trained for deeper and that of all the risks from an air dive to 200ft, PPO2 is towards the bottom of the list that would worry me. He had no idea what risks he actually took on to satisfy his ego / curiosity.

 

[ianr33]

Yeah, they don't have pressurized air in their lungs - no dcs, no oxtox, just blackout...

That's not correct.

Air in freedivers lungs will be pressurized to ambient, and my understanding is freedivers can get DCS. O2 is not a problem due to the brief exposures (And presumably the air in a freedivers lungs has a lot less than 21% O2 in it at the deepest part of a dive)

---------- Post added May 25th, 2013 at 11:27 AM ----------

It is true that 1.2 is the recommended exposure for DIR divers (on the "working" portion of their dives), based on what I have read here on ScubaBoard.

That may well be true. But it's likely aimed at divers spending a couple of hours at depth.

For short exposures on recreational dives, a pO2 of 1.4 seems totally reasonable to me,but of course everyone is free to choose their own limits.

For a 200,or even 250 foot bounce on air, O2 toxicity is a non event IMHO. Narcosis is the real problem. I've done a few 200 foot air dives in perfect conditions. I know I can function well enough to maintain depth,and monitor gas and time. I also know I wouldn't react appropriately in an emergency.

 

[kaerius]

Have you ever seen one drop into the abyss? I was in a group of four once when the Instructor dropped, his wife and his DM just hovered watching, and I dropped down until I hit 1.6 PPO on my Nitrox and hovered. I was not going to chase him. I later learned that I was the only one of the four who not not in on his plan, probably because he knew I'd object. There have been stories of divers who went beyond safe limits to rescue another, and good for them, but that should never be expected.

At least that particular reckless individual had a plan... on my last vacation, there were a couple of polish guys who went down to 60m(200ft) while chasing a shark, their divemaster(instructor) stoped chasing them at 40m(133ft), only blind luck got them back topside with no lasting effects(neither dead nor bent). Sidenote: it was in the maldives, standard tank is AL100, not AL80.

 

[MMM]

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A ScubaBoard Staff Message...

A side discussion in this thread on Oxygen Toxicity has been split off and moved to Advanced Scuba forum here: http://www.scubaboard.com/forums/advanced-scuba-discussions/455187-oxygen-toxicity-discussion.html . Please remember the special rules of this forum and restrict your discussion to the actual incident. Marg, ScubaBoard Senior Moderator

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