Your earlier statement compared solo diving to CCR and cave diving. This statement contains nothing about solo or cave.
You did and continue to represent the loss of the buddy as a decision on the part of the diver. That is just ridiculous. The diver did not make a decision to lose his buddy. Letting go of him physically, in order to accomplish some other required task is not a decision to lose his buddy. If a juggler drops one of his 7 balls, does that mean he made a decision to drop the ball? No. It means that circumstances exceeded his ability to keep control of that ball.
Once again, how much is too much? Commenting in hindsight is easy. The reason we do it is understand the failure point and prevent them next time we go diving. So how many of us will go in low visibility cold lake with a buddy and try to manage their buddy ascent? Please if you do, do it without a deco load. This is training. No need for an instructor. Pretend your friend is incapacitated. If things go sour, he will be able to take over. If visibility is low all the better.
Diving a CCR is more complicated than diving OC. And, ascents are the MOST complicated part of diving a CCR. Gases are expanding all over the place. ppO2 levels are dropping. Injectors are firing to make up for the dropping ppO2 (possibly, if diving an eCCR), which means the machine is adding gas to the loop, which you are already dealing with having it expanding and making you positive.
It's a lot. I have about 80 hours on the loop. That is nothing by the standards of the truly experienced people on here. But, I'm well past being a total newbie and it is still a lot, for me. Taking all that and adding the job of doing it or making sure it's done for your (compromised) buddy, in addition to doing all that for oneself is a LOT.
As stuartv says. Wing, dry suit and counterlung expanding. Times two. Lights. Only two hands. Need to vent at least 2 thing on each diver at any one time requiring hand movement (the wing and the dry suit, while you can vent the loop from the nose - not the incident diver), with the loop of the incident diver at maximum buoyancy ... he is not breathing from it. The you maybe need to have a look at depth gauge and your deco status and maybe ppO2 (not knowing ppO2 will kill you).
It becomes kind of busy. This is why on serious dives, team of three is better: one shoots the DMSB one helps and the other is the trouble diver, still you have no guarantee that separation will not occur. (BTW what is serious for me of for you?) Establishing buoyancy control is main issue, in CCR ascent (I fully support: it is the most complex, task loading and risky part of CCR diving) having a good depth reference is vital. My instructors, they dive at level I cannot even imagine to match, both told me in case of emergency establish a line (from the wreck or to the bag) and if anchored at the bottom, stay slightly positive, in case to the surface, stay slightly negative and monitor the line to see if is becoming slack or too tight and manage buoyancy accordingly.
Same thought here... reduce depth as soon as it's reasonably possible. To quote our local Diving Doc, "We can fix bent. We can't fix dead.".
Apart from that, this sounds like a well-planned and executed dive. Honestly, compared to the CFs that my friends and I carry off ever weekend, this is hard to explain.
Well, while I can agree you cannot fix dead, I have to highlight that diving He (like 18/50) and coming up from, let's say, 60mt 30min dive, unless the doctor is there with a chamber, you would be quite dead before even be out of the water. If you do the Polaris missile ascent, you will be dead no matter what. So, as everything goes, it depends.
I would say that, as planning goes, a bit of risk management and analysis would possibly have improved to outcome. And that is planning. So I do not agree with well planned. Also gas was wron, deciding to do a deep dive with no recent experience was wrong, doing it in challenging (maybe not for them?) environment was wrong.
I did now attach an xls version of the risk management matrix (which can be changed) and a pdf for those who do not have excel. Look at the risk in there, maybe adapt it to your diving and just think about it before going to the dive site. Reassess if condition change.
Doing what one HAS to do to keep oneself from corking, and losing your buddy in the process, does not (necessarily) represent a bad decision on the part of the diver. Unless you simply fall back to saying "buddy diving on a CCR in low viz is a bad decision, period." In which case, well, that's a subjective statement with no real refutation, I don't think, other than, "my opinion differs."
I really appreciate the original post, the translation, and the experienced people who have shared their insights here. Thank you to all of you.
I can agree but if you start saying:
Buddy (vs 3 some) diving;
Low Viz
No recent experience
Deco Dive
Cold water
Narking gas
No DMSB (maybe, not known)
Unfamiliar equipment
Then bad decision .... that probably would have been better. But once again, nobody goes to the dive site to die. Why all of the above made sense at the time the decision was made? Can we guarantee that we will not make the same fatal judgemental error?
Just my reflections on this to contribute to the learning process.
The buddy was maintaining contact and leading the deceased back. Separation occurred when he had to vent his own gear, this implies they were ascending. Yes, I think ideally they should have remained in touch contact at all times. Reality isn't always that simple, I can tell you from personal experience how difficult it is to bring up someone frozen in panic from 115'/35m on OC while controlling both their and your bouyancy. On CCR I've only done it in class from 25'/8m, and that was much, much more involved. It was a bad situation to be in and it sounds like the buddy did what they could.
