US Navy Decompression Table

[impulse]

There really needs to be a solid wall between recreational diving and technical diving. I'm not much in favor of the idea that there is a gray area. Recreational diving really means there is no 'overhead'; virtual or physical. A physical overhead is something like wreck penetration or cave diving. There is a structure that prevents your direct ascent to the surface. You have to live long enough to get out before you can try to go up.

A virtual overhead is a mandatory deco stop. Again, this overhead prevents your direct ascent to the surface without injury. Recreational diving is based on the idea that, at any time, you can make a direct ascent to the surface without injury.

Then there is everything else: deco diving, cave diving, solo diving, wreck penetration, etc. There are training programs for all of these. TDL, among others, has classes for these types of dives. They are high risk and involve a lot more equipment.

So that's where I put the wall between recreational diving and technical diving. No overhead; physical or virtual.

There should never be a time you lose track of your buddy. After all, you are losing track of YOUR backup. If your buddy is farther away than you can swim with no breath, he's too far away. Not one breath; no breath! After all, you don't know you're out of air until you get NO breath. A situation that should NEVER occur, by the way.

Entanglement for recreational divers is a potential problem more in the discussion than in reality. But it does happen and there was a recent fatality here in Calif where a diver got entangled in kelp near the surface. Odd how the buddy system broke down.

The NAUI and NOAA tables are useful in that they provide a "what if" recovery plan. But I don't think they should be used for deliberately overstaying an NDL. There just really isn't any good reason to ever be in a position where there is a possibility of overstaying an NDL.

But that's the point. Notice how these discussions always start with the NDLs at 30m or more? That's because the NDL is so short that people want to figure out how to stay longer. Or, more likely, recover from a screw-up. Nobody ever asks about overstaying the NDL at 40'. Yet there is more color and more to see at 40' than at 100'. Why is it that everybody wants to dive deep? Been there, done that, have photos. But my favorite dives have been in the 30-60' region.

The mindset for a recreational diver should be: I'm not going to overstay the NDL, I'm not going to run out of air and I'm not going to lose track of my buddy. There are other considerations but these 3 things will go a long way toward living long enough to collect Social Security. It's nice having that check auto-deposited every month!

Richard

So I do not need a back up?

 

[rstofer]

I don't think anyone is recommending using the US Navy tables for recreational diving. We just had a long thread about this. Remember, the US Navy diver has support in the form of a medical officer and a decompression chamber. Obviously, there are exceptions (combat diving) but a very brief reading of their diving manual (available via Google) indicates this level of support for working divers.

The US Navy tables have a lot of information re: deco and non-deco dives. You can find a copy on the Internet (I believe) and they are commercially available. But I'm not 20 years old and in perfect health. I won't be using these tables.

I started with the 1985 NAUI tables. The 1987 tables were a little less aggressive and the 1989 tables won't even allow the repetitive dives that PADI tables allow. These newer tables are quite conservative for repetitive dives.

I don't know that PADI or NAUI produce any tables specifically for deco diving. Maybe for some of the specialties but I haven't seen any reference to such tables/documents. Most tech divers use software to plan specific dives. V-Planner is one such program. These dives are planned, they don't just evolve while underwater.

Pick a recreational table, write your adjusted NDLs on a slate and pay them some mind while you dive your computer. Don't exceed the computer NDL (even though the deco obligation will, in all likelyhood, disappear as you slowly ascend) and you should be safe for THAT dive. Additional dives following a computer failure and within the same decompression period (12 hours?) would be unwise. Dive computer user manuals usually provide some guidance on recovering from a computer failure. It is usually of the form: "Don't dive for <xx> hours" where <xx> is often 12 or 24.

But this is far above Basic Scuba Discussions. For folks that are interested, there are more appropriate forums.

FWIW, the NAUI tables are all on one side of the card. No flipping over and over. But NAUI now requires a 30 fpm ascent vs PADI at 60 fpm. PADI recommends (requires?) a 3 minute safety stop while NAUI does not. PADI terminates the dive time when you begin a direct ascent to the surface while NAUI considers the dive time from surface to surface. You need to keep both feet on one side of the river. You can't mix and match... And you need to understand the ramifications of choosing one or the other.

Richard

 

[Cave Diver]

So I do not need a back up?

As long as you are doing dives within the NDL, I think this response should pretty much cover it.

If your computer fails, you find yourself tangled up in fishing line and your buddy has gone missing it's time to take up golf. Do a slow ascent to 15' then stay there as long as you still have air.

Seriously, I think you're worrying way too much about the wrong thing. Like fire diver stated, there are other skills that you should probably polish first.

 

[HowardE]

Why would a rec. diver consider using the Navy tables at all then?

Exactly

 

[Blackwood]

There really needs to be a solid wall between recreational diving and technical diving. I'm not much in favor of the idea that there is a gray area.

In favor or not, that's how just it is. There is no line between definitely bent and definitely not. There's a wide range of stuff. What doesn't bend you one day may bend you the next. It's as gray as the stupid overcast sky.