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Now, while we are getting a bit off topic - hose lengths were the starting point - I have to comment on this. Doing it was simply not dangerous - at no time was anyone in an OOA situation (In contrast, I would agree, had he started the dive with no gas at all, that would have been a bit on the edge. But that wasn't the case.) Posting this experience is definitely not dangerous. If there is concern as to what a new diver might do as a result of reading something in a thread here, then we need, IMMEDIATELY, to close SB because there is simply too much information / misinformation being put up. In fact, we probably should take down the Internet altogether, or have government censors assigned to decide what is safe to post and what is not.
Again, let''s make sure the statements are accurate and factual. One diver (the LOA diver) had a fully functional, working air supply, with 500 psi in an AL80, at all times. That was always a back-up for him, and for whomever he was sharing air with at a given time. If the donating diver had an equipment malfunction, for example, then the two of them still had the LOA diver's gas supply available to make a normal ascent. If that is considered a problem - e.g. a diver has an equipment malfunction at the end of a dive, and has to share his buddy's air to surface - then we should change the fact that we (often) dive only a single cylinder. If 2 divers cannot make a normal ascent from 50 feet, in benign conditions, sharing air from an AL80 with 500 psi at the start of the ascent, I would hazard the opinion that they should not be in the water - at all. But, in addition to that back-up, there were 6 divers in the water, with a combined air supply of 400 cf at the start of the dive, and 77.4 cf at the end of the dive.
NOT true, at all. Both divers (the LOA diver and the one he was sharing air with at any given moment) had air. If the donating diver at a particular point went OOA, the two of them still had the air in the LOA diver's cylinder (not to mention the other 4 divers in the immediate vicinity). Statements like this contribute to my concern about our sometimes un-thinking adherence to 'rules' or 'guidelines'. If you don't think 500psi in an AL80 (12cf) is an acceptable reserve - for a normal air-sharing ascent from 50 feet, to answer your previous question - then what would you consider acceptable? 1000 psi? When diving with a buddy, do you (both) therefore always surface with 1000psi? If so, good for you. I don't personally find that to be necessary, but 'do as you wish'. Seriously - can a competent, experienced diver execute a CESA from 50 ft? Probably. So, having 12 cf of air to share during a normal, controlled, 30 fpm ascent is easily an acceptable reserve - for ME, and for the others on that dive. But, as I have said several times, if that is not enough for YOU / another diver, that's certainly your decision and I won't fault it.flots am:
Not at all. I don't think what the DM did is 'abuse' in any way. This is not dis-similar to the Bonaire experience that I brought up. As you describe it, the Cozumel diver was not OUT of air, merely letting the DM know that s/he was getting low on air - which could have meant they were down to 1000psi, for example. If the DM has a good / low RMV (as many Caribbean DMs seem to have) and plenty of gas, why not share air for a bit, to allow that LOA diver (and the rest of the group) to extend the dive? I have also seen this from time to time in the Caribbean.
The reasoning may also never be apparent because the reasons for starting the rule / practice to begin with have long since disappeared, but people continue to do things, without thinking about why.
Very reasonable. I would agree. But, what is the 'margin' that is actually being shaved? What is the substantive safety difference between two divers being at 50 ft at the end of a dive, with two cylinders showing 500 psi on the respective SPGs, and two divers starting a dive with one cylinder showing 500 psi and a second cylinder showing 3000psi, if the intent is not to use gas from the 500psi cylinder unless necessary? There is simply nothing wrong with planning an air share dive, if the sharing diver has a back-up sufficient to terminate the dive - at any time - and ascend safely without sharing. There is a big difference between a 'trust me' dive, and a planned, air-share dive. If the SPG(s) is / are off, then whether the 6th diver started with 500 or 3000 is completely irrelevant. Two divers could go still go OOA at the same time at the end of the dive, and the same situation would result. What one of them started with makes no difference whatsoever. Air you have already consumed is not a resource (any more than depth above you, or a full cylinder on shore).
Exactly! Thank you for agreeing with, and reinforcing, my point. The conditions and the situation have to be considered. How do YOU define 'safely', for example? For that matter, how do you know that your SPGs are not both 'off by a couple of hundred PSI'? And, by the way, that is exactly what we did on the dive in question - maintained enough gas to get ALL 6 of us safely to the surface from any point in the dive.
That is exactly right. It is an emergency procedure. It remains as a possible action in an emergency. There was no intent to use a CESA during our dive, unless there was an emergency - that was no different from any other dive. Just as with ANY dive, we knew that such a maneuver could be attempted, if necessary. On every dive, I think about whether a CESA would be even feasible, under the particular conditions applicable at that point, and plan accordingly. I used it as an example of contingencies that are available, not as a statement of what was in a plan.
Interesting thought but it is not really a reinvention. Yes, some REQUIRED procedures have been eliminated, by some agencies - the 'doff and don' as one example, or buddy breathing as another. Yet, we still have DM candidates practice buddy breathing. Why? Because the skill may be useful, because mainly it helps future dive professionals build confidence. (How about requiring certain divers in training - DM candidates - exchange gear - mask, fins, BCD - underwater, while buddy breathing? Is that too dangerous?) Quite a few people still do 'doff and dons' for fun, for the same reason - it builds confidence, enhances skill, etc. We are also talking about an activity that is not required for anyone. Individuals make their own decision whether to participate in a planned air-share dive, on the basis of their skills and experience.
Again, what is the safety margin that is actually being materially shaved? A diver starts a dive with 500 psi in an AL 80 - no less gas than he would have when he begins his ascent at the end of a dive. At the first point where sharing air is not an option, he still has the option of doing exactly what he would normally do - end the dive and ascend normally. Would it be shaving a margin to have six divers start a dive with AL63s instead of AL80s? One answer would be - it depends on the dive', and I would agree. But, if the answer is, 'Yes. It would shave the margin', should we then start all dives with only HP100s or larger cylinders? The primary difference in this case was that an experienced, capable diver intentionally started a shore dive - in benign conditions where simply ascending to the surface was a continuing option - with less than a full cylinder, after discussing it with 5 team mates, and making a specific plan. No margins were materially shaved.
All time when two divers have two independent air sources with about 900-1000psi (in AL80 equivalent) in each with two second stages on each, I think this dive is safety enough.
Now, those are interesting questions and I have to say i have never considered such a possibility.
On one hand, I think it would be absolutely phenomenal if the majority of divers could get to the point where they felt so comfortable sharing air - with a 7' hose or with a 40" hose - that this could become a legitimate possibility. That would be great (the level of comfort, not the complacency). On the other, I don't really believe - but I could be wrong - that it (complacency leading to OOA situations) is a necessarily likely or predictable outcome of simply using a long hose. But, now that you have brought it up, I will have to think on that one. Thanks.
