Thanks everyone for the great feedback! It's been really interesting to read through so far.
But, I avoid situations where the dive guide is driving my dive profile. I either dive with a guide that I know in advance is very conservative; or I dive with my buddy, or if I am following a guide with no specific known buddy, then I do only shallow "swim around the reef" type dives.
In an ideal world, I'd do this, absolutely. But my diving generally takes me to places without buddies -- I'll take a day from a non-diving holiday and go diving leaving my friends to do their own things. If I limited myself to "swim around the reefs" i'd never see any cool wrecks!
Square things, sit in the kitchen, thats it; tables. Dive planning for the use of.
I can plan a dive on a table, no problem. They were still all the rage when I first qualified in 2000! But i'd rather use computers for multilevel, multi-stage dives as it reduces the chances of me messing up.
You had about 750 liters of air remaining, enough to bring a (calm) buddy to surface, so no big deal, especially since computers' NDL are very conservative.
Why don't you dive nitrox?
I don't dive nitrox yet because I'm still working out my technique on air, and I don't want to add to my task loading or potential points for me to mess up before I feel ready. Plus, so far, I've been able to access everywhere I need to. It's my next course, along with a rescue course.
When the DM told you to "wait there"..it sounds a little like you were sort of on your own in an over-head environment. Add to that, being uncomfortable with the dive plan and pushing NDL past your comfort zone.. (if I got that right)
Honestly, pushing NDL past 1 minute remaining exceeds my comfort zone. To credit the DM, he never "left me on my own" -- he was never more than ~4m away (a distance I was comfortable I could cover fast in an out-of-air situation) and I was comfortable with the plan as-briefed. But as-briefed didn't include any mention of accruing 20+ minutes of mandatory deco!
You should have given the 'Thumbs Up' signal and made it clear you wanted to end the dive. I agree that you were not in any real danger from deco, but it sounds like you were not comfortable.
I'm leaning towards agreeing. I've always been loth to give the "thumbs up" signal (i've only terminated a dive early once in 75 dives), but in this situation it was probably the right thing to do.
If there had been an issue with another diver.. Would you have been asset to help? ..Or an additional accident risk, if the whole thing went sideways?
Also, this sounds like the perfect dive profile for Nitrox. Especially when diving out as a single add-on diver. It would give you a lot more flexibility on types of dives you can do, with a better margin of safety.
I'd like to think I'd have been an asset, but I'm relatively inexperienced compared to the DM and most divers (although some holiday divers I've seen... I might as well be a DM next to!). Nitrox is my next course; above.
You were, frankly, put in a rather compromising position. It is one thing to accumulate 5 minutes of calculated 'deco' obligation at depth, which almost always clears on the ascent. But, you accumulated 20+ minutes, per your post, which didn't clear on the ascent. And, required you to stay down for ~25 minutes to clear the computer. Play out possible scenarios: What if you had not had enough gas? What if there had been an underwater emergency that thwarted the DMs plans to have everybody stay down and clear their computer?
One of the reasons I call myself a "conservative diver" is that I do play those scenarios out in my head a fair amount; I read Diver Down a few years ago and that's made me much more mindful of "what if" scenarios. That's one of the reasons I feel so uneasy about how this dive went.
As to what you might have done differently: it is a difficult call. Personally, I think you should have been more aggressive in ending the dive. But, that is not a criticism, just an observation, in hindsight (which is always wonderful). It is NOT within the domain of authority - or competence for that matter - for a dive guide to intentionally ignore a situation where a diver's computer is racking up a calculated deco obligation on a recreational dive. Simple as that.
I think you're right in that I should have been more aggressive in terminating the dive. I'll learn that for next time.
The take-away lesson: next time you are in a similar situation - preparing for a guided, deep dive: have a chat with the guide on the surface before the dive. Let them know that you are going to follow your computer if you run out of NDL. It is your dive, your computer, your health.
Absolutely; to make it even more embarrassing I've said similar to other buddies of mine when prebriefing on other dive trips. I should practice what I've preached.
So far, it's working fine. Set 'normally' it's annoying on multiple dive, multiple day trips. I've seen people hang theirs off the down line so it wouldn't freeze up, or sit out dives for the same reason. Unless you know a better way to tame the 'excessively' conservative nature of the Suunto (my opinion, not shared by everyone, but shared by many
) we'll keep doing it that way.
What if my UWATEC goes TU? Then I have my wife's 'messed with' Suunto, or my backup Favor. I'm comfortable with that. Having a computer croak on a dive is never fun but you just wander up and do a long safety stop.
This scares the bejeesus out of me, but I don't think I'm qualified or experienced enough to comment further, except to say that if you're going to ignore your computer, why dive with it in the first place?
I wouldn't call 1 hour (I assume OP's "1h" stands for) SI "short". IIRC my PADI table, it takes you half way down the pressure groups. It'd be interesting to see what the 1st dive actually was and run it by the RDP: it may well be that 6 min NDL is within a couple of minutes of the table NDL and so not that conservative.
I meant 1 hour. I don't have a comms cable for the computer or I'd happily share the profiles.
Thanks again, I'll keep checking back tomorrow for more info
Now I have to figure out how to write the dive up in my logbook...