Filmmaker Rob Stewart dies off Alligator Reef

[RichardC]

Sorry, stupid question. Shouldn't the leading tissues be accounted for on the subsequent dive and be taken into account in the dive profile, computer or planning software?

Not a stupid question at all.

I think the message with the slow tissues is that they are not perfectly well understood by the current models. The NEDU study showed a higher than expected incidence of DCI on the deepstop profiles and, if I remember correctly, Dr Doolette was suggesting that fairly low levels of supersaturation sustained for a long time (i.e the area under the graph - integral supersaturation for the mathematicians) were having a significant effect on the DCI incidence, but that the mechanism was unknown at that time.

I know many people are trending away from deepstops as a result of that study.

 

[uwxplorer]

I'm not at all sure that all the computers and planning software give exactly the same results when running the same algorithm. I would be interested in an independent comparison.

By definition of an algorithm, any implementation should give the same results, provided all input parameters are equal. I have based my comparison on those I could read off of the presentation. There might be some secret fudge factor in Trudive...

 

[Steve_C]

As somebody who does scientific computations for a living there was a good point earlier (well good to me anyway). All algorithms are approximations based off experimental/theoretical data. The diver him/herself was never part of the experiment. So for a given diver there can be extra or less conservatism for another diver. If the model keeps getting applied during a day the more the error builds up. This may have no relevance to this incident but pushing things out to three, four, .. tech dives a day is probably operating way outside the data the alrogithm was verified on and extraplolating outside the data is known to be risky in many situations.

 

[scubadada]

By definition of an algorithm, any implementation should give the same results, provided all input parameters are equal. I have based my comparison on those I could read off of the presentation. There might be some secret fudge factor in Trudive...

I've always thought this too. Actual implementation may be somewhat different.

 

[Cowfish Aesthetic]

pushing things out to three, four, .. tech dives a day is probably operating way outside the data the alrogithm was verified on and extraplolating outside the data is known to be risky in many situations.

This is a very good point. I suspect that there is very little (if any) scientific data on dive plans like this, because it sounds like no one dives them. In diving, as in life, if it hasn't been studied, you're the guinea pig.

 

[KevinNM]

I think one possible issue with multiple deco dives in one day is that the slow tissues will not be fully off-gassed between dives. There is some evidence (and I'm thinking of the NEDU deepstops work here) to suggest that the effect of tissue loading in the slow tissues is not fully understood and that what would once have been considered a low saturation may matter more than previously thought.

With a deep bounce dive shortly after your second dive couldn't you also get bubbles from the previous dives compressed enough to make it into the arterial side?

AJ mentioned this a few days ago.
Why We Do Not Bounce Dive After Diving in the WKPP | Global Underwater Explorers

 

[jonathan d iseson]

What bailout were each diver carrying? Pulling the hook in a strong current is strenuous. Did they take all or any bailout since they were just pulling a hook. Btw there are approaches to this that eliminate that issue. So many folks to ask question s to. To me the day after u get your cert diving with your instructor said student is still a follower, not forward thinker. But as it appears you will never know what happened as no one involved will give it up

 

[uwxplorer]

As far as necklaced reg, I tried it myself with the rEvo and didn't find it convenient. Mostly because of routing issues, as you can pull the DSV and the strap will yield without a problem. And you wouldn't do that downward, but upward.
The debate on the strap is about whether it would have prevented Rob from sinking, assuming he did not remove his DSV voluntarily.

 

[RainPilot]

As far as necklaced reg, I tried it myself with the rEvo and didn't find it convenient. Mostly because of routing issues, as you can pull the DSV and the strap will yield without a problem. And you wouldn't do that upward, but downward.
The debate on the strap is about whether it would have prevented Rob from sinking, assuming he did not remove his DSV voluntarily.

Agree completely. IF however he was hypoxic on the loop then he would have removed his DSV ASAP, I can see a scenario where someone would not think of closing it before ripping it out to get a good lungful of atmospheric. I am definitely going to review my diving because I honestly am not sure that I always close the DSV before removing it on the surface. I think I do but now I will make sure.

 

[uwxplorer]

I am under the impression that you do not react well to hypoxia. You just pass out. If your mouthpiece falls off your mouth, it is game over very quickly. If not, because of a gag strap, the time before going under might be long enough that someone notices you are in trouble and comes to help.
That's really all there is to it and where AH's recommended practice might be fatally flawed. On the other hand, most if not all other units do not come with a gag strap - in particular, AP units come with a strap, but not a gag strap...
rEvo is pretty adamant that the gag-strap is one of the key safety features in their unit. Maybe because they are not very flood recoverable, sure, but tox underwater, and without a gag strap... well, read above.