Recreational Scuba Deco Diving

[tmassey]

And I think that this understanding is why so many of us are frustrated by those who want to resurrect the concept of “recreational deco“.

Their argument of, “We did it in the past! Why can’t we do it now?“ ignores how much has changed in the interim. The gear, training, length of NDL dives, the way NDL is calculated, even the way NDL is measured is now all completely different! A lot of the margin that those old assumptions included has since been wrung out with longer NDLs, shorter surface intervals, and more aggressively tracking dive characteristics on a second by second basis.

Unfortunately, you can’t take advantage of all of those changes and then say, “Well, that requirement that was thrown away in order to enable those improvements – I want that back too!“ You *can* say that, but it’s not logically accurate. And unfortunately, it’s a mistake that can get you hurt.

ETA: And there’s no “Banning“ of deco. There’s no SCUBA police. It’s just that all of the training and limits are based on the fact that there’s no deco. And that was removed for actual, real benefits: longer NDL, shorter surface intervals and simplified, modular training. But if you change the underlying assumptions (by re-adding deco), the rest of it is logically invalid. It’s not that it’s banned, it’s that there’s no rationale that you can use to do it in a logical fashion given modern recreational assumptions.

Of course, if you want to go all the way back to Navy tables, there’s nothing that stops you from doing it. But you can’t mix RDP and deco. And you can’t mix training that has at its core “If all else fails, go to the surface“ and deco. It was eliminating deco that made those other practices safe. If you re-introduce deco, you have to also make changes to address your changing assumptions.

And frankly, I couldn’t care less if you (the proverbial "you", not any specific poster) do 30 minute dives to 150 feet on air with only a single aluminum 80 and your manliness. Do it: just don’t ask the rest of us to think you’re clever. And realize that we are also going to point out the risks that such a dive includes and alternatives that address those risks.

 

[tmassey]

Or, to say that last part *much* better: (First 15 seconds, in Fred Thompson's perfect mix of southern drawl and distain):


(Or a text version... First quote, from Big John)

 

[scubadada]

Hi @boulderjohn

I like your story. I dived from 1970-80 using USN tables. We did not do deco diving without the training or the gas (single steel 72). Skip ahead to 1997 and I dived the PADI RDP. In 2002, I bought my 1st computer, running DSAT, that was the end of tables for me.

The PADI RDP became available in around 1987. The PADI Wheel and the DSAT deco algorithm on Oceanic (Pelagic Pressure Systems) computers both appeared in the early 1990s. There are some small differences between the PADI RDP and the DSAT computer algorithm.

Computers calculating multilevel dives, and then, the addition of recreational nitrox, are two of the most dramatic advances in diving

 

[rx7diver]

When I began this thread I was thinking: It's extremely likely that many people (like me) are in situations where obtaining EANx and oxygen fills is difficult or impossible, and it's extremely likely that at least some of these people deco dive without using high-octane nitrox or oxygen as deco gas (that they cannot get).

And then I asked who among us does this? And how, exactly, do we do it?

Simple--well, if you accept my premise, that is.

Some of us seem to be arguing that this (i.e., deco diving without using high-octane nitrox or oxygen deco gas) is NOT happening, because ... um, why, exactly? Because, people now know how to deco dive using high-octane nitrox or oxygen deco gas? This seems as nonsensical as arguing that people are no longer diving deeper than an END of 100 fsw (say) because people now know how to dive with helium mixes!

At any rate, eighteen pages of posts is long enough for this thread, I think.

Thank you to all of you who contributed.

Safe Diving,

rx7diver

 

[Celt]

Thanks @mac64 and @tursiops.
You just filled the information I was missing, and now it is clear where and when deco was expulled from the field of rec diving.

Angelo the old tables had a serious flaw. They were developed for young healthy navy personnel. A diver followed me into a wreck to film us working. I went 5 minutes ahead of him and he left the bottom 3 minutes before me which left me with 8 minutes more bottom time and I was working. We both did the same deco. 15 minutes after getting in the boat he lost the use of his left arm and within 5 minutes he was paralysed down his left side. We dressed him and brought him back in the water for an hour and a half emergency deco. Back on the boat he said he was fine but 2 hours later he had to be brought to the chamber for Oxygen recompression where he recovered.

 

[tursiops]

Some of us seem to be arguing that this (i.e., deco diving without using high-octane nitrox or oxygen deco gas) is NOT happening, because ... um, why, exactly? Because, people now know how to deco dive using high-octane nitrox or oxygen deco gas? This seems as nonsensical as arguing that people are no longer diving deeper than an END of 100 fsw (say) because people now know how to dive with helium mixes!

Mistake Number One. You have not understood most of what people are saying, it appears, possibly because it does not agree with your bias.

At any rate, eighteen pages of posts is long enough for this thread, I think.

Mistake Number Two. YOU do not get to decide when this thread has ended. It is likely to go on and on, possibly for years, with more and more people disagreeing with you. Sorry.

 

[rx7diver]

Mistake Number One. You have not understood most of what people are saying, it appears, possibly because it does not agree with your bias.

Mistake Number Two. YOU do not get to decide when this thread has ended. It is likely to go on and on, possibly for years, with more and more people disagreeing with you. Sorry.

@tursiops,

I'm sure you aren't deliberately trying to be obtuse. I have no bias one way or the other. Numerous people in this thread responded to answer my OP. There were/are several side conversations, sure, as always seems to happen with these SB threads. But, I learned much from people who responded on topic.

Take Care,

rx7diver

 

[BRT]

@tursiops,

I don't use an octopus, either. Why would a solo diver require an octopus? And I don't use a PDC (except sometimes to record my dive). I use published tables.

Honestly, I am not asking about best practices, or agency training standards, or certification levels, or anything else, except what is it that people actually do (regarding RSDD)? Simple question, I would think.

rx7diver

A friend of mine recently had his reg start breathing water. He had no octo and was alone. Made a quick trip up from 140.

 

[MichaelMc]

Some of us seem to be arguing that this (i.e., deco diving without using high-octane nitrox or oxygen deco gas) is NOT happening, because ... um, why, exactly?

Two possible explanations:
- The members seem mostly US based. US agencies teach no-deco or are then (mostly) focused on accelerated deco. And, possibly from skipping the light backgas stage, US divers may not be doing the math on the limited saving from accelerating what is already a small deco amount, if we are in the light deco realm. People who took accelerated deco likely have O2 available near them.
- The UK does teach backgas deco as the natural progression, and the few of them chimed in.

Your description reads like backgas deco, possibly light.

For me,

1. Never, as not qualified by any of the classes that teach it.

The light backgas deco classes are mildly appealing. I think I might use it on occasion on the fly, provided I had ample independent reserves. Such as with the dive planned principally as no-deco but with a backgas deco variant. My normal rig is sidemount, so I have independent air sources. AN/DP provides more options though.

If deco was the principle plan, I might stay longer and carry 50 or 100% if it was available, so not your scenario. If no O2, I could see doing a planned light backgas deco dive, obviously given contingency gas, thermal, etc. and certification for it.

2. Shore
3. Salt
4. Solo mostly
5. Sidemount doubles. (Backgas is a good enough term, the meaning is obvious.)
6. Depth, cold level. I'm far from the NDL on EAN32.
7. Sightseeing

 

[NothingClever]

When I began this thread I was thinking: It's extremely likely that many people (like me) are in situations where obtaining EANx and oxygen fills is difficult or impossible, and it's extremely likely that at least some of these people deco dive without using high-octane nitrox or oxygen as deco gas (that they cannot get).

And then I asked who among us does this? And how, exactly, do we do it?

Simple--well, if you accept my premise, that is.

Some of us seem to be arguing that this (i.e., deco diving without using high-octane nitrox or oxygen deco gas) is NOT happening, because ... um, why, exactly? Because, people now know how to deco dive using high-octane nitrox or oxygen deco gas? This seems as nonsensical as arguing that people are no longer diving deeper than an END of 100 fsw (say) because people now know how to dive with helium mixes!

@rx7diver - I think if your posts had a been a little more straightforward (ie., decompression on back-gas alone versus accelerated decompression), you might have had more favorable responses.

I don't mean to be an obstructionist but I'm not putting "recreational SCUBA deco diving" into an abbreviation. The more you write it, the more difficult it is for me to believe that you weren't hoping for it to take root as validation of your niche perspective.

Regardless of what gas I have and what depth I'm at (below about 8m), I'm either decompressing or I'm not. And I'm either trained or untrained. And I'm either diving with the appropriate redundancy to adhere to virtual ceilings or I'm not.

Just get out there and dive. Your daughters probably value the example of an active father doing adventurous stuff and for that I think you should be commended.

Happy New Year.