Basic rules broken become near miss

[Yeason]

So there has been a lot more activity that I'd expected here, I'm going to try to answer as many questions and clarify as much as possible. First off, part of my beating myself up is my training, I should have known better and did a stupid. But as many have said I've learned from it. I haven't shared this with many because I'm frankly embarrassed I even allowed myself to get into this situation. For those who have asked I am an OW Instructor and have hypoxic trimix training. I have around 400 recreational dives and probably in the neighborhood of 30 technical dives so I am admittedly a newer tec diver.

I think I mislead everyone into the belief that there was no plan, this is not the case, but I felt in hindsight that we should not have been pushing as deep as we did. The plan had been for between 40-45m max depth with around 10 minutes of deco time as I was with the "experienced group". I don't want to risk implicating anyone so I will only say that this was in fact in Europe (no burst discs as mentioned above, hence for lite tec dives considered acceptable) in an area where we were going to see the Gorgonia sea fans which only occur after around 40m. We did in fact reach the bottom but it's largely volcanic rock (not loose) and sand, so unfortunately no options to grab ballast although this is a good point and something I will keep in mind. On this note there is some misunderstanding, the entire dive was not at 53 meters, we generally followed the contour and that was the max depth.

For those talking gas planning, that is one of the bigger flaws of some of these dives, the locals tend not to plan these dives properly. For me, from experience I would have been well within my usual gas plans. For this dive I would have gone to around 45m for around 10min, with a rather conservative (for me) SAC of 20L/min gives me 74 bar used on a 15L tank leaving 126bar for descent, ascent, and reserve. Typically I do these dives and return with at least a third of a tank of air.

In the interest of transparency and learning, here is the profile: Imgur

If anyone has a question I've overlooked or not answered bring it up as I am still quite willing to go over it. For those who have questioned some of the sense of this dive or the actions taken, that's why this post exists at all... I did a stupid and I'm learning from it and hoping others will do so as well.

 

[saxman242]

The plan had been for between 40-45m max depth with around 10 minutes of deco time

In retrospect, would you dive this plan again without a fully redundant air supply?

 

[lermontov]

For those who have asked I am an OW Instructor and have hypoxic trimix training. I have around 400 recreational dives and probably in the neighborhood of 30 technical dives so I am admittedly a newer tec diver.

30 tech dives ? does that include your extended range course? you must have just about done your extended range and adv trimix back to back

 

[rjack321]

for some reason your profile image isn't visible?

 

[Yeason]

In retrospect, would you dive this plan again without a fully redundant air supply?

To me in some respect this goes back to the "Is an H Valve fully redundant" and I would argue it is. Actual tank valve failures are incredibly rare and in the area I was diving we did not have burst disks. I always made sure that I could reach both valve handles so in case of a failure short of catastrophic tank failure I could still isolate and surface. Plus I would still have a fully capable buddy with air supply. Previously I'd done this type of dive at least a dozen times. So without the problems on this dive,with the right planning, yes I would do it again. However, I prefer a full tec setup including twins and stage when this is possible.

30 tech dives ? does that include your extended range course? you must have just about done your extended range and adv trimix back to back

You are more or less correct, I did a few tec dives between the extended range and the Tec Trimix. Even though my Trimix course went flawlessly and my instructor was rather happy with my performance I am still going slow and intending to take a step back. This experience was a good humbling reminder that I will always be learning. While I would be willing to plan and execute a dive even to ~80m (my personal record) I am hoping to build more experience in the 40-60m range before making more dives into deeper ranges.

 

[Yeason]

Also not sure why the image is not appearing so here is the direct link Imgur

 

[lermontov]

I am hoping to build more experience in the 40-60m range before making more dives into deeper ranges.

i think this is a a good plan -please take more gas

 

[Celt]

I think people have different ideas of what a dive plan is. If I strayed even 1 meter deeper than my planned max depth or overstayed my max time at depth I would immediately move to backup plan. At depth small errors can mean big differences in gas usage and deco times.

 

[Scuba Cobra]

While I would be willing to plan and execute a dive even to ~80m (my personal record) I am hoping to build more experience in the 40-60m range before making more dives into deeper ranges.

You're seriously still willing to plan and execute an 80m dive after what just happened?you have done it "dozens of times" and the only reason it wasn't ok this time was because you didn't plan and had a weighting issue?

I honestly think that's a terrible idea and you're teetering the line to becoming another statistic. It's like we are reading a story in Gareth Locks book about Normalization of deviance in action..

 

[Kay Dee]

1) do people really consider that an H valve qualifies as sufficient redundancy for technical diving?

No not at all! Nor is a single tank appropriate by any means on a planned deco dive, not matter how short the planned deco!

'After all, if the burst disk fails (I've seen that happen on a cylinder just laying there), what are you going to do?

Pray your buddy - if you have one - has enough air to share, otherwise your SOL.

2) given Dr. Simon Mitchell's maximum gas density of 5.2 g / L (Alert Diver | Performance Under Pressure) which translates to a max depth of air to 100 feet / 30 meters, do people think it is a safe practice to exceed that with diving deep on air?

Depends on how much deeper, and the equipment you use (I was fortunate enough to always use top of the line breathing equipment, i.e. regulators). I can't speak for others, but I and many other people I dived with for over 30 years had no problem with exceeding these so-called 'limits'. But they were very experienced, repeat very experienced, divers well exceeding that 30m 'limit' on air.

If so, what are your thoughts on Dr. Mitchell's advice?

Good advice to the general diving population, and something that we all at least should be aware of, especially when on CCR's. (And no, on CCR I had no reason to use air deeper than 30m, so I didnt, but often, in some places around the world they did not have helium, so then I certainly did on OC).

Given his expertise in dive medicine, what is your reasoning for disregarding his recommendation?

When I was doing it there were no such 'recommendations' for a start. But, personally, I habitually exceeded these so-called 'limits' over the years and never had the problems now being associated with same. That does not say they don't exits at some point though! And of course, before someone chimes in - as they will - and says "just cause I 'got away with it / deviated from the norm' does not mean it's OK", then by all means your welcome to that opinion. I am not trying to convince anyone to dive deeper than 30m on air, if that's what they believe is the line in the sand (er, water) then stick with it! But after all, as some would have you believe, one shoe (or fin / 'flipper') actually does not fit all, AFAICT.

What do you know that he doesn't?

Very little! For a start, he knows way more than I ever will on gas physiology, nor would I counter his advice to the diving public. Simon and I know each other personally - as a matter of fact, I taught him his civilian CCR course - and back in the day we dived off and on together (photo below shows him coming off an 80m deep small trawler wreck off Brisbane circa early 2000's IIRC).

But make no mistake, I am not recommending here you or anyone else does it (i.e. dive deeper than 30m on air), but you asked a series of questions and I gave truthful answers from my own experience / perspective is all. And none of what I say above is meant in any way as disrespectful to Simon (aka Dr Mitchell) or his colleagues in developing said 30m recommendation.

HTH.