Shallow Decompression Dives

[ScubaSteve]

This is a good point and yet another reason why the education is critical to doing it safely. My computer (a Suunto Cobra) is capable of telling me what my deco requirements are if I exceed my NDL.....however that does not mean I should go out and try to extend my bottom time beyond NDL without proper training. I think the term "casual deco divers" to me implies that there is no planning involved. With this thread, we are hopefully giving the reader that wants to extend their bottom time, the ways to safely PLAN a shallow deco dive (this in the form of which courses to take).

The other thing that "casual deco" divers usually lack awareness of is the need for redundancy. It is pretty easy to go to 100 feet for 25 minutes and conduct short deco on a single 80 cu ft tank for anyone with a half decent SAC rate. But if your SPG blows or you get a sudden free flow, and you don't have the necessary gas redundancy, you can easily find yourself travelling up a certain creek with a shortage of paddles...

 

[Bob Sherwood]

GUE teaches several methods for planning and all are referenced back to Deco Planner. GUE teaches that ALL dives are decompression dives, starting with the open water course. Decompression ranges from a minimum to a maximum. The current version "Deco Planner 3" has both Buhlman and VPM side by side for comparison. You can get a wide range of acceptable/unacceptable profiles with all of the available software. As mentioned, individual and team choices are important planning issues. Education and Experience together create the best ability to make good judgments reguarding individual and team diving. Great posts. Best, Bob

I have no formal training from GUE, but my understanding is that DecoPlanner is still their primary decompression tool with Deco On The Fly ("Ratio Deco") being emphasized for contingency usage.

 

[Blackwood]

Thanks Bob. I'd forgotten than DP also does VPM.

What's the official word regarding GUE's current view of Ratio Deco as it pertains to pre-planning dives?

 

[rjack321]

With this thread, we are hopefully giving the reader that wants to extend their bottom time, the ways to safely PLAN a shallow deco dive (this in the form of which courses to take).

UTD's "tech1" (which has a 130ft depth limit, doubles, 25/25 trimix, and O2 bottle), otherwise such courses do not really exist in North America.

Although many intro deco courses could be conducted shallower than (e.g. 160ft) course limits and you should discuss such a program with an IANTD or TDI instructor (who are given quite a bit of latitude) who might be willing to host a <130ft Adv. Nitrox+deco course.

CMAS and BSAC may address these topics at the AOW-ish level (probably minus the redundancy most people feel is required nowadays). BSAC also has a darn aggressive set of deco tables and I am not sure they are a good resource.

 

[ArcticDiver]

Given that all dives are decompression dives, whether taught that way or not, and that DCS is rare it seems to me there is too much emphasis on the need for extensive "special" deco training. Much of what I've read in other venues seems to be more for marketing of a course than something needed.

Now, I'm not an "old time" NAUI diver. But, my initial training was NAUI and even at that level I understood how to use tables to plan a dive, any dive. That a planned stop had to be at some other depth than 15' was of no consequence from a profile planning point of view. A planned dive is a planned dive.

Since then I've been introduced to a variety of thought themes from a variety of teaching agencies. Each has had its' own take on dive planning. But, physics is physics and the characteristics water don't change. So, these have done more to reinforce the idea that from a profile point of view all dives have the same factors; none of which are complicated.

Where the thought train goes astray is mixing in the needs of certain kinds of diving, usually deep, and the desire for faster decompression, usually requiring gas switches. It further goes astray when desired dive methods, such as team diving, are thrown into the mix. Now, we are going beyond the physics of diving to other matters that we have chosen to affect the dive.

So, to me, this is an issue of clear, analytical thinking, not of any special training.

 

[JamesMottUTD]

UTD teaches decompression theory and practices starting at our Recreational 1 (OW) level. Discussion of the dissolved and bubble models are presented very early on as we feel that understanding how to build a proper ascent strategy is an essential tool that should be taught early and built upon as the diver progresses, rather than teaching something new and or different later. Further application of deep stop strategies, ratio deco strategies and how to shape the overall curve are a major part of Recreational 2 (AOW/Nitrox) and they go hand-in-hand with what gas the diver is breathing and why. Recreational 3 starts to bridge the gap between recreational and technical diving. These &#8220;tech-reational&#8221; dives introduce the use of Helium in the breathing mix as well as how to apply ratio decompression beyond the NDL zone. Ratio Decompression is also a separate course that anyone can take, and learn to incorporate into their diving at whatever level they are at. It breaks all of the current knowledge of various decompression theories down into an understandable format that you can start to disect. As with all of the UTD courses you will see that quality experience in the area of training is paramount to readying the diver for future education.

 

[Thalassamania]

Just remember, it may seem counter intuitive but, making a shallow dive that is rigorous enough to get you into a decompression status is a far less forgiving situation than making a deep dive that results in the same decompression obligation.

 

[Rhone Man]

According to DAN more people get bent on long dives rather than deep dives.

At least that is what my instructor said. Sounds right.

 

[Deefstes]

Given that all dives are decompression dives, whether taught that way or not, and that DCS is rare it seems to me there is too much emphasis on the need for extensive "special" deco training. Much of what I've read in other venues seems to be more for marketing of a course than something needed.

...

So, to me, this is an issue of clear, analytical thinking, not of any special training.

I hear what you're saying but on the other hand, is it really sensible to be teaching OW students all the extensive gas planning that accompanies deco diving? Sure, explain to them why gas planning becomes important when you do deco diving but I'm not sure it really is necessary to put them through the graft of calculating air consumption, cylinder size, air usage on ascent corrected for average depth during ascent, air usage on stops etc.

Isn't it better to just teach them that 50 Bar is a safe reserve at which to terminate your dive? That would suffice for the ascent and any safety stops that you might choose to make. Then one day, when you start doing deco diving, we'll go into the details of planning the profiles and calculating the air requirements.

I mean, working out a dive profile and required stops is easy, you simply read it off the tables with a little bit of extra knowledge when it comes to repetitive dives etc. But calculating the air requirements is far more involved and in my (inexperienced and humble) opinion, a way more important aspect of deco diving.

 

[CamG]

Greetings ScubaSteve! A big thank you for this thread and another for all who have posted! This is what makes Scuba Board great, the wealth of information that is represented.
I have been researching Deco and acclimating to the terminology. This thread has been very interesting and educating. It is an example of how divers world wide are all a part of one community that though we might have differences we can still help one another!
To the OP and all the other posters thank you!
CamG keep diving....keep training....keep learning!