Past NDL. And then this???

[sea_otter]

I don't really want to drag the thread off on an irrelevant tangent.

Fair enough. I'll drop it out of respect for the OP.

And to the OP, by the way, thank you for sharing! Always interesting and thought provoking to read accounts of things that didn't go quite right. Definitely takes guts to share them on the internet when people are going to jump all over you and criticize every detail of what you did, but anyone who claims to have never made a stupid mistake diving either is a liar or doesn't dive.

 

[KenGordon]

I am not familiar with BSAC or CMAS courses, but surely pushing limits deeper (to 40 or 45 meters through a PADI or TDI class) isn't the right answer for a beginner diver with 50 dives.

I still consider myself very much a beginner diver, but I found myself frequently bumping up against NDLs and "fixed" the problem by switching to Nitrox. Later I found myself bumping up against NDLs again, and I decided then it was time for more training. In hindsight, it was too early to start. This was after approximately 130 dives (I think the minimum for the class was 100, so I barely qualified), a couple dozen of them in doubles. I had also taken a Fundamentals class in this time. It took another few months and another 30 or so doubles dives to get to a point where I had the skills required for the class. I also have an instructor who would not let me progress until I could demonstrate these skills (and I'm thankful for that).

Rushing into technical dive training doesn't seem like a good idea.

The OP is already doing dives which result in deco. He just doesn't understand why and how to deal with the issue. That is what he would learn on an entry level, back gas deco course. It is not all about depth. Time and repeat dives will also lead to deco. Knowing what to do if you make a mistake, and how to avoid those mistakes, is the stuff to learn. Unfortunately the history of how diving has been taught (especially in the US) has left those skills as some sort of forbidden fruit.

I am not suggesting he learns how to do twinset and a stage diving, just simple backgas deco so he can handle it when it happens.

For reference look at Sports Diver - British Sub-Aqua Club

Annoyingly, the entry level TDI and PADI courses start with a deco cylinder which is all a bit 'technical' for the OP's requirement, but even if he never dives with one he will understand how deco works and so be able to make better choices.

 

[Miyaru]

The OP is already doing dives which result in deco. He just doesn't understand why and how to deal with the issue. That is what he would learn on an entry level, back gas deco course. It is not all about depth. Time and repeat dives will also lead to deco. Knowing what to do if you make a mistake, and how to avoid those mistakes, is the stuff to learn. Unfortunately the history of how diving has been taught (especially in the US) has left those skills as some sort of forbidden fruit.

Exactly my thoughts. The OP has been touching the NDL for a week. During the OW course, the instructor should teach what a computer will show you when you (accidentally) exceed the NDL limit, specifically the difference between ascent time and stop time on the display:

...
I thought the computer was telling me: Look, you will have to spend 4 mins deco at 3 meters while it was telling me, within 4 minutes you have to be at 3 meters ! It makes a lot much more sense to me now.

Once your number of dives go up and you gain more experience, touching the limits becomes easier. Touching it doesn't mean crossing it.
Before crossing the NDL, first understand why that limit exists and what it means. And once you decide to cross it, plan it upfront.
Planning starts with understanding (the art of) decompression.

 

[stepfen]

It is very hard to determine what your learnings from this experience have been by reading your replies. What do you feel is the most important new information you now have?

The most important new information I now have is "next time do not post such things in SB !"

I am kidding of course. I learned lot's of things, I am still getting more by the newer posts and I am sure I am still missing several important things. But I can't highlight the most important. Probably the most important thing was that now I know how to handle this situation in the future, and by "situation" I don't mean only going past NDL, but the whole chain from approaching NDL, avoiding going past, and in case I go past it, how to deal it. Or maybe to make it more general the whole chain from choosing DM/buddies, to planing, diving style, etc etc... It also became very apparent to me how important it is to become independent diver (I don't mean to dive alone - but be able to handle the dive alone) . During the event I was paying more attention to what other divers did or how they reacted instead of making sure how to protect my health the better I could.

 

[boulderjohn]

During the OW course, the instructor should teach what a computer will show you when you (accidentally) exceed the NDL limit, specifically the difference between ascent time and stop time on the display:

The OP revealed that he took the table version of the course. In his OW course, he would have learned how to use tables, but he would not have learned about computer operations.

 

[scubadada]

I've been a member of SB for nearly 13 years, there have been many threads just like this one, running out of gas or "unexpectedly" going into deco. This is not rocket science. Pay attention to your SPG or AI computer for gas supply, pay attention to your computer for NDL and know how to use your computer and what it's telling you. There really are not many acceptable excuses. You are responsible for yourself. If you can't do this, I would say, that you were inadequately trained to dive independently or are simply ignoring what you were taught.

 

[Neilwood]

The most important new information I now have is "next time do not post such things in SB !"

I am kidding of course. I learned lot's of things, I am still getting more by the newer posts and I am sure I am still missing several important things. But I can't highlight the most important. Probably the most important thing was that now I know how to handle this situation in the future, and by "situation" I don't mean only going past NDL, but the whole chain from approaching NDL, avoiding going past, and in case I go past it, how to deal it. Or maybe to make it more general the whole chain from choosing DM/buddies, to planing, diving style, etc etc... It also became very apparent to me how important it is to become independent diver (I don't mean to dive alone - but be able to handle the dive alone) . During the event I was paying more attention to what other divers did or how they reacted instead of making sure how to protect my health the better I could.

It does sound like you are taking the lesson the right way. You are thinking more responsibly about your diving which is no bad thing

 

[sea_otter]

The OP is already doing dives which result in deco. He just doesn't understand why and how to deal with the issue. That is what he would learn on an entry level, back gas deco course.

Until you posted the link, I did not realize that such classes existed. The "recreational" deco class I took involved doubles and a stage.

By the way, I got curious and noticed that stepfen had provided his dive profiles. Here is the dive in question (with gradient factors at what I would consider a very conservative setting). Subsurface is also taking into consideration nitrogen loading from previous dives in the log entry shown.

Should there have been better planning and execution? Sure. Better understanding of what to do in a situation like this? Absolutely. And through this post, I'm sure he's learned a lot. I have as well.

He spent 35 minutes hanging at 10 feet and the computer didn't clear. That's insane. I have no idea what algorithm the Cressi Leonardo uses, but it is obviously not an effective tool for any dive involving even minimal deco (unless it can be set in a depth gauge mode to use with a pre-written plan).

 

[sea_otter]

And here it is with the settings I'd normally dive:

 

[BenjaminF]

@sea_otter , could you maybe explain why you would use those particular GF settings (if you're already comparing between them...)?