"I'm so conservative..."

[MichaelMc]

I’m so conservative,
I breath O2 before the dive, and come up before I reach surface nitrogen saturation.

 

[KenGordon]

You don't calculate your deco based on being able to get gas from your buddy.

Isn’t that like “you shouldn’t calculate your ascent from 40m based on being able to get gas from your buddy.”?

 

[KevinNM]

I'm going to buck the tone of this thread a little, by starting with the initial post. Unless I missed something, we know nothing about this diver. He indicated that he was experienced and that he dove conservatively. But most of the posts in this thread seem to disbelieve that, and portray him as an unskilled cowboy. Is it not possible that he was in fact highly skilled and very experienced? Just because he didn't roll out a sheaf of c-cards does not mean he doesn't know what he's doing. If he is confident in his air consumption, he may well have been allowing for lots of gas to make his ascent safely. The OP doesn't state where they were diving, but assuming it was nice warm, clear water he may well have known exactly what he was doing.

Again, unless I missed it, I didn't see anything about his gas supply being depleted. Not everyone uses the same amount of gas obviously. He may well have had buckets of gas left.

As for his definition of "conservative" and using 30/85, he is going to go into decompression sooner than many. But assuming he does the required deco, and perhaps adds a few minutes for good measure, that is, at least in my book, "conservative". Changing the settings in the computer doesn't change a thing in the body of course. Would everyone feel better if he'd set his Petral at a more aggressive GF, avoided "decompression" showing on the screen, and surfacing after a 3 minute safety stop. To my mind, that is NOT conservative at all, just because the computer says "go"...

All of this is to say that while agree that there are many shortcomings in the divers methods, I think there's a little bit of judging going on.

I'm his buddy. He's got 10 minutes of deco obligation and I run out of air due to say my burst disk blowing out. So now I'm breathing his air, at a pretty good rate due to all the exitement. How is this story going to end?

 

[rongoodman]

Isn’t that like “you shouldn’t calculate your ascent from 40m based on being able to get gas from your buddy.”?

No, because a basic assumption of recreational diving is that you always have immediate access to the surface.

 

[Neilwood]

I'm going to buck the tone of this thread a little, by starting with the initial post. Unless I missed something, we know nothing about this diver. He indicated that he was experienced and that he dove conservatively. But most of the posts in this thread seem to disbelieve that, and portray him as an unskilled cowboy. Is it not possible that he was in fact highly skilled and very experienced? Just because he didn't roll out a sheaf of c-cards does not mean he doesn't know what he's doing. If he is confident in his air consumption, he may well have been allowing for lots of gas to make his ascent safely. The OP doesn't state where they were diving, but assuming it was nice warm, clear water he may well have known exactly what he was doing.

Again, unless I missed it, I didn't see anything about his gas supply being depleted. Not everyone uses the same amount of gas obviously. He may well have had buckets of gas left.

As for his definition of "conservative" and using 30/85, he is going to go into decompression sooner than many. But assuming he does the required deco, and perhaps adds a few minutes for good measure, that is, at least in my book, "conservative". Changing the settings in the computer doesn't change a thing in the body of course. Would everyone feel better if he'd set his Petral at a more aggressive GF, avoided "decompression" showing on the screen, and surfacing after a 3 minute safety stop. To my mind, that is NOT conservative at all, just because the computer says "go"...

All of this is to say that while agree that there are many shortcomings in the divers methods, I think there's a little bit of judging going on.

He is not diving conservatively as, given any issue with his or his buddy's gas, he does not have direct access to the surface due to the "soft" ceiling of the deco that he has built up. Boulderjohn has already confirmed that no discussion took place about deco prior to the dive and there were no discussions about reserves or back up air sources (as would normally be required for any dive with a ceiling). He also confirmed that the diver hadn't given it a thought. We are not talking about an insignificant deco amount such as 1-2 minutes which will quite possibly clear on ascent, we are talking about a fairly significant 10 minutes or more (he would possibly have built up more if Boulderjohn hadn't called it when he did).

As soon as there is a ceiling (hard such as a surface in a cave or wreck or soft as in deco), there should be a discussion about reserves/back up gas which will allow for one or both divers to complete the deco stop at elevated breathing rates given the loss of one persons main gas source.

I'm his buddy. He's got 10 minutes of deco obligation and I run out of air due to say my burst disk blowing out. So now I'm breathing his air, at a pretty good rate due to all the exitement. How is this story going to end?

I would say potentially with the brown substance hitting the air moving equipment at a rate of knots!
There is either a skipped mandatory deco by ascent to the surface or they take the chance of running out of gas during the ascent due to lack of reserve.

 

[Stoo]

I don't disagree with what you guys are saying at all in a "normal" buddy pair. My overall impression of this buddy pair, is that they were no such thing. The "offending" diver was essentially diving solo, and in a cavalier fashion. The OP was trying to behave like the responsible buddy and arguably had a somewhat stressful dive trying to do the right thing.

My comment about the guys "conservatism" was only aimed at his deco profile, not in how he conducted the dive overall.

Had I been the OP, I think I would have told the guy he was on his own after the first dive.

 

[Hoag]

Personally, I think that there might be a couple things going on here that have "reached a nexus" so to speak. It appears that @boulderjohn 's buddy might have been a competent diver from the point of view of "his skills were very good--he did indeed look to be quite experienced" but he either forgot, never learned or disregarded some of the basics.

The first and most obvious of these is the premise that recreational diving is no deco diving. That is why the NDL is stressed during trg and why it is featured prominently on virtually every recreational dive computer. To deliberately do a deco dive has taken your dive out of the realm of recreational diving and into the fringes of technical diving. Based on the info that was given, we have no way of knowing if he was properly trained, but I strongly suspect he wasn't.

The next aspect that was overlooked, ignored or disregarded was the concept of "Plan your dive and dive your plan". If he was planning to do a deco dive, he should have (at the very least) let his buddy (@boulderjohn ) know what his plan was.

It is one thing to incur a deco obligation. I have had it happen to me (on the 3rd dive of the day with a very conservative computer) but when it happened, I followed what my computer said and then I sat out the 4th dive. I wasn't trained in deco diving and I thought that since I had ventured into an area where I wasn't trained that sitting out the last dive of the day might be the prudent thing to do. (FWIW, our dive profiles were not aggressive at all, 50-70 feet for 45-60 min with a little over an hour surface interval between dives on air.) As I was saying, it is one thing to incur a deco obligation, but for you to consistently dive profiles that this obligation has now become a routine part of your dive means that it is time to get the training that will give you the tools to do this safely.

 

[scubadada]

@Hoag,

Why, exactly, did you sit out the 4th dive after satisfying the, I assume, short, deco obligation on the previous dive using your "conservative" computer? Was this based on physiologic concern or was it a punishment for violating your training standards? How about your buddy, did he or she also go into deco, or were they diving a more liberal computer? What did your buddy do on the 4th dive?

 

[Hoag]

@Hoag,

Why, exactly, did you sit out the 4th dive after satisfying the, I assume, short, deco obligation on the previous dive using your "conservative" computer? Was this based on physiologic concern or was it a punishment for violating your training standards? How about your buddy, did he or she also go into deco, or were they diving a more liberal computer? What did your buddy do on the 4th dive?

Yes, it was a very short deco obligation. IIRC it was something like 5 or 10 minutes at 10 feet, so little more than an extended safety stop. I sat out the 4th dive because I wasn't trained in deco and I thought that it was better to be safe than sorry. It was not some sort of self-imposed punishment, I simply did not want my exuberance on one day to have the potential to become a physiological issue later in the week. (The time wasn't totally wasted. I was at the bar with a margarita a little before everyone else.) I was the only one whose computer registered a deco obligation, and since we were in a group, my buddy dove as a "three ship" with 2 other members of our group for the last dive that day. For the rest of the week, I made a point of staying shallower than everybody else to ensure that this did not become an issue again and that I wouldn't have to miss any more dives.

FWIW, I sold that computer after that one trip.

 

[scubadada]

@boulderjohn Hi John,

Many good points have been brought up in this thread.

In your initial description, you state the dives were at the limits of recreational diving. Before the dive, did you and your buddy explicitly agree to dive within rec limits, i.e. no deco, and/or was it a boat rule? If the answer to either is yes, then he purposefully violated one or both of the agreements. If the answer is no, he may of simply been diving his usual "conservatve" profile. The wisdom of doing so has already been extensively discussed.

Out of curiosity, were you prepared and would have been allowed to dive solo? This is my most effective strategy for avoiding instabuddy surprises. In this case, your buddy would have been paired or grouped with others.

I understand about agreeing to buddy. In my experience, having the buddy limited by gas and/or NDL is far more common than them outstaying me. This also brings up another group of questions regarding appropriate management