More than "Advanced", but not really "Technical"

[Dive-aholic]

I see the value of educating recreational divers in light deco theory, but I also see the threat of removing the "fear factor" from the NDL. I still believe that setting conservatism high and entering light deco is better than an aggressive dive plan that takes one right up to the NDL.

I agree. But where do you draw the line. If someone is doing aggressive dives that take them right up to the NDL it's likely that if you give them the tools to do light deco they will start pushing those limits and start doing more involved deco...all on recreational gear. There has to be a line somewhere. Single tanks don't belong in decompression diving.

 

[lowviz]

...//... it's likely that if you give them the tools to do light deco they will start pushing those limits and start doing more involved deco...all on recreational gear. ...//...

And that is the "unintended consequence" of my approach. The original idea was to cool someone's jets by adding in all the conservatisms. Doing so puts them into deco on very typical recreational dives. So I decided to get input with the downside of dealing with deco on recreational gear.

I've reconsidered my position and will not proceed with this. However, I just can't let go of the original premise. Problem is, it truly is a "Pandora's Box" kind of fix...

 

[victorzamora]

lowviz, I totally get where you're coming from. In a perfect world, I'd completely support teaching OW divers light deco theory just to get their heads wrapped around the physics. I think that diving a very conservative computer (or tables) and diving light deco is a perfectly valid dive methodology. As we all know, EVERY dive is a deco dive.....but not every dive do you get a virtual ceiling. However, with the recent incident in FL.....it seems like tempting people is the WRONG way to go.

I think a safer way of doing it is to teach something similar to what PADI has on their RDP, a bare-bones, super-simple guid. If you blow your NDL by <5 minutes, immediately ascend to 15ft for 8minutes or 15minutes for >5min past NDL. Or, follow your computer. Either way, you're done for the day. You should NOT have done that, you do NOT know what's going on with nitrogen in you physically, you need 12 (or 24 or whatever) hours to offgas. Do not do too much excercise for 2 hours after. Keep an eye out for bendy-like symptoms.

I think one thing that should be taught more aggressively is proper gas planning. It may need to be more of an AOW topic, but I think Rock Bottom/MinGas or other gas planning techniques would be incredibly helpful. Heck, teach 'em that they're responsible for their gas AND the gas of their buddy. Diving to MinGas/RB is much less likely to get them into deco anyway, and even if they do they'll have more gas to cope with it.

 

[Doomnova]

I first learned about deco diving from my Scientific diving course I took as it is mentioned on the dive tables we have to use. Myself I am very conservative with my dives and have never gone into deco and when I do my safety stops I always run 5 min stops. Now going into what I learned it is good to know what is going on and understanding what deco is and how it relates to every dive. Do I think its a good idea to arm every person with what deco diving is? Mmm hell no. We see so many people who are very poor divers and are not conservative. I have the SAC rate (sits about .42-.45) to hit NDL's so the info is useful to me in a situation where deco planning may come into play with scientific diving. Most people would see ok lets do a light deco dive to stay deep and longer without the equipment and we will see even most divers becoming statistics and doing profiles long before they are ready to actually be in tech diving.

I think the information while useful for understanding can very easily lead to many burned fingers and missing fingers.

 

[tursiops]

PADI's rule is simple to use. All you need to remember is "3" and "5". Your safety stop is 3. If you exceed NDL by less than 5 minutes, ADD 5 to 3 and get 8 minutes at your safety stop. If you exceed by more than 5 minutes, then MULTIPLY 5 by 3 and get 15 minutes at your safety stop.

Then stay out of the water for 6h or 24h as mentioned previously. 6h lets you (a) mostly clear, and (b) many DCS symptoms have a chance to display; 24h lets you (a) really clear, (b) allows most DCS symptoms to have time to display, and (c) puts you in the penalty box (no diving for a day) to slap you on the wrist for being so clueless about your profile and gas.

For those of you who like numbers, here is what MultiDeco says about exceeding your NDL. The PADI EANx32 NDL for 80 feet is 45 minutes, with a mandatory 3min safety stop; MultiDeco (ZHL16-B with conservatism 80/80 GF) says the NDL for 80 feet is 41 minutes, with a mandatory 3min deco stop at 10 feet, so that's pretty similar (but not identical because the PADI tables and ZHL16-B are very different models). If instead of 41 mins, you stay 46 mins (5 mins over), MultiDeco says you need a 10-foot deco stop of 5 mins. 10 mins over means a deco stop of 6 mins; 15 mins over means a 9 minute deco stop; 20 mins over means 12 mins deco; and 25 mins over means 15 mins deco. Compare that with the PADI rule......the PADI rule is easy, and may very well be what you need if you do that clueless-about-time-dive.

But!!
25 mins over the 41-min NDL, at 80 feet, means (even with a really good SAC rate) you need 150 cu ft of gas to do the dive.....two (!!) AL80s, nearly drained dry.
Even the NDL dive (41 mins) needs more than a single AL80 for a gas supply.

Punch Lines:
- deeper diving can be dangerous to your health
- deeper diving and approaching NDLs (especially with Nitrox) can be REALLY dangerous to your health, because you can run out of gas before you run out of bottom time
- do the deeper, longer dives on air.....now NDL is the limiting factor, not tank size

 

[rx7diver]

All (especially younger and/or newer divers),

As a matter of fact, not so long ago [non-accelerated, or non-technical] deco diving was taught routinely as a part of one's *initial* open water course. Students were tested over required-gas calculations, surface-interval calculations, procedures/protocol, etc., etc., etc.

My initial course was in 1986, taught primarily from the *6th* edition (copyright 1985) of "The New Science of Skin and Scuba Diving," which included a chapter on deco diving (using the US Navy Standard Air tables). Presumably the five earlier editions (*1st* edition is copyright 1957!) presented decompression diving, too.

My course also emphasized that open water divers are NOT to engage in decompression diving.

To my knowledge, none of my fellow student divers was seduced&#8212;ever&#8212;by this early exposure to deco diving, to deco dive. On the contrary, I think we were all left with an extremely informed notion, that deco diving requires a lot more than the usual approach to [recreational] scuba diving safely provides. Yet, we had the tools to relatively safely complete a dive if we somehow found ourselves in an obligatory deco situation.

I'm having a difficult time understanding some of the recommendations posted in this thread, to censure this type of teaching early on to open water students.

Safe Diving,

rx7diver

 

[DevonDiver]

I agree. But where do you draw the line. If someone is doing aggressive dives that take them right up to the NDL it's likely that if you give them the tools to do light deco they will start pushing those limits and start doing more involved deco...all on recreational gear.

I agree... but being uncharacteristically optimistic.... I see that the benefit of training itself might help 'shape' the mindset of that diver.

I believe 'very aggressive' recreational diving generally stems from a lack of balance between training and experience. Just as too much training, with too little experience (card collectors/zero-to-heroes) causes problems, so does the opposite.... high experience and too little training.

In essence, 'a little knowledge is a bad thing', reinforced with enough experience to 'normalize' the aggressive and/or dangerous approach and falsely reassure the diver that everything is okay. In actual fact, they've been rolling the dice for years and simply getting away with it through luck.

Entry-level tech courses, across all agencies, place a high degree of focus on 'technical diving mindset'. There are plenty of experienced, aggressive, divers out there who would benefit from an introduction to that mindset. You can't shift those people's perspectives over the internet, or by chatting... but you can do so in the water.

I guess it all depends on the instructor. A successful one, IMHO, qualifies students who have gained a healthy respect for decompression through effective education.

 

[lowviz]

...//... Entry-level tech courses, across all agencies, place a high degree of focus on 'technical diving mindset'. There are plenty of experienced, aggressive, divers out there who would benefit from an introduction to that mindset. You can't shift those people's perspectives over the internet, or by chatting... but you can do so in the water. ...//...

And a solid course that is based upon the introduction to that mindset is exactly what I would like certain divers to experience. In an honest way, not by pretending to start down the road to tech and then bailing out after a crossover course. Several divers that I have in mind have no intention of ever going tech or buying tech gear, however, they would be interested in such a course and would benefit greatly from same.

I started this thread with an imperfect approach to an ill-defined problem hoping to get some thinking done out loud. The first step in problem solving is to clearly define the problem. I just now feel that this has been done. This is the power of a global discussion that includes a diverse collection of opinions and experience.

 

[DevonDiver]

And a solid course that is based upon the introduction to that mindset is exactly what I would like certain divers to experience. In an honest way, not by pretending to start down the road to tech and then bailing out after a crossover course.

The Deep Diver course... could'a, would'a, should'a...

If not that, what purpose does it really serve? Other than to provide a piece of plastic to get you on dives (precisely the mindset that one would hope to discourage).

I started this thread with an imperfect approach to an ill-defined problem hoping to get some thinking done out loud. The first step in problem solving is to clearly define the problem. I just now feel that this has been done. This is the power of a global discussion that includes a diverse collection of opinions and experience.

I'm not of the opinion that new courses should be created to fill this void. The void, itself, stems from a failure originating in the existing courses.

If (more) agencies recognized deep, wreck (and some others) as advanced recreational activities, then the scope of that training could increase. Cavern is often touted as a worthy 'advanced' recreational course for diver development. What differentiates cavern from deep or wreck? In practical terms, or in respect to increased risk, nothing. In reality, it is industry regulation and community acceptance... 'caves and caverns' are sanctified... you need 'good' training... you need redundant gas....you need drills and skills and protocols... you need training.

Designating 'advanced' recreational activities solves that conundrum. It recognizes a consistency of increased hazard and a requirement for higher level recreational diving skills, knowledge and experience.

Exemplary instructors already treat these courses with that respect. A minority of agencies do so also... but, where that exists, it is mostly driven by an anticipation that the particular training is a step on the ladder towards higher levels. Other agencies, the major ones, don't have that ladder.... they plateau. Open Water...flat level. AOW/Specialties/Rescue...all exist on a single flat level. And then the leap to technical... a vast stride, for which many students are unprepared (by training, if not by experience).

 

[lowviz]

The Deep Diver course... could'a, would'a, should'a...

I'm guessing you mean PADI, but it fits what I experienced in IANTD also. I immediately drew a line through that one for the issue at hand, it starts out as a problem I don't want you to go deeper...

...//... I'm not of the opinion that new courses should be created to fill this void. The void, itself, stems from a failure originating in the existing courses.

Yes, but Tec40 sounds just like something that was created to fill a void.

If (more) agencies recognized deep, wreck (and some others) as advanced recreational activities, then the scope of that training could increase.

If you want to go deep or dive wrecks...

Cavern is often touted as a worthy 'advanced' recreational course for diver development. What differentiates cavern from deep or wreck? In practical terms, or in respect to increased risk, nothing. In reality, it is industry regulation and community acceptance... 'caves and caverns' are sanctified... you need 'good' training... you need redundant gas....you need drills and skills and protocols... you need training.

BTDT. Cavern is THE single most under-appreciated course that exists in dive instruction. Did you really put it in the same sentence with deep and wreck?

Designating 'advanced' recreational activities solves that conundrum. It recognizes a consistency of increased hazard and a requirement for higher level recreational diving skills, knowledge and experience.

"Advanced" is a funny word to me, it mostly means that I didn't go and find a new hobby after trying OW...

Other agencies, the major ones, don't have that ladder.... they plateau. ...//... And then the leap to technical... a vast stride, for which many students are unprepared (by training, if not by experience).

Couldn't agree more. So for the practiced recreational diver, is PADI's Tec 40 an introduction to the technical mindset, or is it a gateway course to PADI's "Deep" progression?