One dead, one missing (since found), 300 foot dive - Lake Michigan

[uwxplorer]

It varies. rEvo are inherently negative even before the counter lungs flood (amount depends on the frame size and SS vs Ti), this makes them nice in the sense of less weight on a belt but it can lead to being overweighted easily depending on your exposure suit / bioprene levels.

My Poseidon unit, in a jacket BCD with AL tanks needs about 3 lbs to sink it with empty counterlungs, the counter lungs are pretty hard to fully flood in that unit. When I dive drysuit with it, I have a steel plate and steel tanks, that makes it around 5-10lbs negative depending on gas weight and plate thickness. Some of the SM CCR units are pretty close to neutral by design.

Generally, most units on the market will be negative if you manage to fill them completely with water, some more than others.

Not the physics that works around this part of the world. If you are submerged, you have to be properly weighted. With drysuit that means less weight is needed on a rEvo than on a Poseidon, but from there on filled counterlungs remove the same amoint of buoyancy on any unit (probably more on the Poseidon).
As mentioned many times, it is likely that the unit had nothing to do with the accident, as in so many cases.There is not much room for any problems at those depths.
Heart breaking.

 

[doctormike]

research submarine escape, they are cesa's. mind you the bottom time is not generally what you will see in tech diving. It could be close to someone who bombs the floor and then does a
Polaris

I think that the point was that a CESA from a 300 foot dive would likely involve a lethal amount of decompression stress. The interior of a submarine is 1 ATA, so there is no nitrogen ongassing prior to flooding the escape chamber, right? But yes, once the escapee equalizes to ambient pressure and begins the ascent, it's basically a CESA.

 

[John C. Ratliff]

So here is the part I'm totally missing in all of these discussions. A dive to 300 FSW requires a significant amount of bailout gas consideration, being OC or CCR. I have not in any report seen any mention of whether they were or were not carrying bailout cylinders, however their experience level would suggest they had, or if it's been deployed and used or available but not touched. If, and pure speculation, they did not have the necessary amount and mix of bailout gas, why were they allowed to dive? If they had, how come 2 divers miss the opportunity to bail out, it seem rather strange since the 1st protocol for CCR emergency is to bail out in case af critical failure. Did they plan on shared gas emergency and somehow the bailout failed. If the planning was shared emergency gas as a four diver team, did every member carry an amount for save bailout at the MOD.
I do realise that in a panic or when hypoxia / hypercapnia start setting in you can totally miss the opportunity to bail out, much less be coherent and doing a controlled ascent before you become so positive and have a runaway ascent (looking like a ESA to others), also totally plausible imo.

Just my 2c worth thinking about what is not said.

The video of them on a different wreck shows them wearing the CCR, plus two slung AL 80s, while going around on their scooters.

SeaRat

 

[jfe]

The video of them on a different wreck shows them wearing the CCR, plus two slung AL 80s, while going around on their scooters.

SeaRat

That is why I said their experience indicate that they would, and after posting I watched the video, however it still leaves a lot of unanswered question that would remain unanswered from this tragety.

 

[Griffo]

So here is the part I'm totally missing in all of these discussions. A dive to 300 FSW requires a significant amount of bailout gas consideration, being OC or CCR. I have not in any report seen any mention of whether they were or were not carrying bailout cylinders, however their experience level would suggest they had, or if it's been deployed and used or available but not touched. If, and pure speculation, they did not have the necessary amount and mix of bailout gas, why were they allowed to dive? If they had, how come 2 divers miss the opportunity to bail out, it seem rather strange since the 1st protocol for CCR emergency is to bail out in case af critical failure. Did they plan on shared gas emergency and somehow the bailout failed. If the planning was shared emergency gas as a four diver team, did every member carry an amount for save bailout at the MOD.
I do realise that in a panic or when hypoxia / hypercapnia start setting in you can totally miss the opportunity to bail out, much less be coherent and doing a controlled ascent before you become so positive and have a runaway ascent (looking like a ESA to others), also totally plausible imo.

Just my 2c worth thinking about what is not said.

Medical emergency? One has an episode,the second attempts a rescue and all **** hits the fan? Having all the gas in the world isn't going to help if one of them can't breathe (IPE) or has another issue (stroke, heart attack etc).
All guesses, but having enough bailout doesn't guarantee you can make it to the surface.

 

[rjack321]

research submarine escape, they are cesa's. mind you the bottom time is not generally what you will see in tech diving. It could be close to someone who bombs the floor and then does a
Polaris

yeah but subs are at ambient pressure, not diving

 

[beester]

personal curiosity, why do you continue to trimix OC dive 250 to 300 ft deep? Is it to reach specific wrecks? And do you prefer OC at those depths for ease of use compared to rebreather, or another question do you prefer rebreather but sometimes do OC to dive the same as dive partners?

Mmmm long story short... I switched to rebreather (with some others) in 2017, because I was increasingly diving deep and a lot of times in mixed teams (oc, jj, rb80 (scr)), both of which became kind of a hassle to deal with. I didn't immediately fall in love with the machine, for me it was just a tool.

Then life changes happened (became a father, moved to Italy), so the amount of deep diving dropped of sharply for a while. I had only done about 50 dives on the unit and still didn't really like it, didn't feel comfortable to start diving it on deeper wrecks. With the limited amount of diving I could do switching to OC was like putting on your favorite pair of old jeans. Even thought about selling the unit, and just keep diving OC.

But I'm forced to change my mind and really start putting the rebreather hours in, because frankly I'm running out of OC buddies to do deeper dives with. I understand the benefits but also the dangers of rebreather diver reasonably well... and yes on deep dives, with the exception of a total rebreather failure or scrubber breakthrough, you have many more options to manage issues... still doesn't mean I have to like the bloody machine ;-)

I hope this makes sense... !

PS: A very good buddy of mine (previous RB80 diver now switched to JJ) told me... you probably don't like it yet because you haven't used it yet in anger (on a deep dive)... he told me he only started falling in love with it, once he started using it on deeper wreck and cave dives.

 

[chillyinCanada]

Am I correct in understanding that the other buddy pair were down on the ship at the same time as the deceased? And if so, at this time, are they either not saying if they saw/know anything, or do we know that the surviving buddy pair were unaware?

 

[beester]

So here is the part I'm totally missing in all of these discussions. A dive to 300 FSW requires a significant amount of bailout gas consideration, being OC or CCR. I have not in any report seen any mention of whether they were or were not carrying bailout cylinders, however their experience level would suggest they had, or if it's been deployed and used or available but not touched. If, and pure speculation, they did not have the necessary amount and mix of bailout gas, why were they allowed to dive? If they had, how come 2 divers miss the opportunity to bail out, it seem rather strange since the 1st protocol for CCR emergency is to bail out in case af critical failure. Did they plan on shared gas emergency and somehow the bailout failed. If the planning was shared emergency gas as a four diver team, did every member carry an amount for save bailout at the MOD.
I do realise that in a panic or when hypoxia / hypercapnia start setting in you can totally miss the opportunity to bail out, much less be coherent and doing a controlled ascent before you become so positive and have a runaway ascent (looking like a ESA to others), also totally plausible imo.

Just my 2c worth thinking about what is not said.

Jfe, there are just too many variables to get a clear view, or make a good analysis of the accident. Even if they find both divers, all the equipment all you can do is make assumptions and rule out some clear cases (equipment malfunction, scrubber breakthrough, wrong gasses... obvious stuff). It's still not going to give you info on the decision tree leading to the incident, and what was done / how the divers reacted to this cascading flood of issues, leading to their ultimate demise.

All I know is at that depth, that water temperature, your margin of error is quite low. All you need is a small cause that is not handled properly to increase stress/breathing rate... at that depth WOB is high (no matter what gas they were using), causing CO² buildup, and before you know it you are struggling to make the right decisions.

A close buddy of mine once had a CO² hit on his RB80, he told me that he literally wouldn't have been able to switch to bailout, he was so hyperventilating in the end that the thought of removing the loop from his mouth was impossible... what saved him in the end was that he had a BOV and another buddy switched him to bailout.

 

[rjack321]

The video of them on a different wreck shows them wearing the CCR, plus two slung AL 80s, while going around on their scooters.

SeaRat

2 slung 80s is not enough BO from 300ft even under the most optimistic consumption rates / deco obligation unless (at a minimum) O2 was hung from the boat.
But there's no reporting of BO being deployed, used or not. So there's really nothing to say about having bailed or not.