This has got a bit out of hand. As far as I'm concerned, the recent twist in this thread wasn't really about your diving skills, atj, whatever those may be. If you will recall, we were talking about solo diving, which led me to recall and post links to the thoughtful articles which Bob Halstead wrote on the subject of buddy diving and the practice of surfacing to relocate a missing buddy some years back. I thought these articles might be of interest here because so many divers seem to assume that buddy diving is the sine qua non
of safe diving and that other practices and procedures learned during their 4-day McPADI course (like ascending to locate a missing buddy, wearing a snorkel on mask) are both safe and universally applicable to almost all dives. Some of us question those assumptions.
You asked me if I could explain why ascending and then reascending might be a bad idea, and that's what I tried to to in my last post. I also made it clear that I personally didn't think these considerations were particularly critical on a dive to 10 meters, which is apparently what you were concerned about, and reminded you that the original comments about the practice of ascending and redescending were explicitly in reference to dives to "non-trivial depths".
I confess that I can't really follow the distinction you seem to be trying to make between a "full dive" and something less than a full dive. Is a full dive "emptying the tank", finishing off a memory card, or what? In any case, I don't think I've ever seen any reference to a distinction between "full dives" and "half" or "quarter" dives in anything I've ever read in modern dive decompression theory or practice A bounce dive to 30 meters is still a 30 meter dive in any model that I know of. And nobody assumes that your dive to 30 meters is a square profile with the entire bottom time spent at max depth.
If you can provide a reference to the legitimate authority which you are basing your argument (if that's what it is) that multiple bounce (or sawtooth) dives to depths of 30 meters or more do pose additional risks of DCS compared to an orthodox profile, then I and many others would be very interested to see it.
If you don't know of any reputable authority, then I would urge you to be very cautious about inventing your own decompression theory and/or rules for handling profiles and ascents, and to be doubly cautious about sharing your speculations with others who may not have the experience and knowledge to distinguish practical realism from dangerous nonsense. I just noted that your sig references a link to your logged dives since certification in 1978, totalling roughly 300 dives over the past 30 years, and roughly 100 dives over the past three years. The vast majority of your dives appear to be limited to depths of 11-15 meters, and there are only a handful of dives to 30 meters, none deeper. Nothing wrong with any of that, and it's nice to see that you've been diving for a long time, and not to be harsh, but I don't think 300 lifetime dives, mostly to less than18 meters, is the kind of experience that would make you an authority on what makes certain dive profiles safe or unsafe, do you?
I hope it's clear by now that this discussion wasn't really about you or your dive skills, and also that I really don't care what you and your buddy do or don't do, at any depth. Bounce up and down all day if you want. But if you really believe sawtooth dive profiles are not really dangerous under certain conditions that you believe you somehow have the knowledge and experience to figure out on your own, then I'm not sure I'd want to talk about it in a forum like this one, and definitely pas devant les enfants
Edited by frogfish, 05 August 2007 - 07:18 PM.