max depth?

[cantlogon]

the water doesn't suddenly turn into acid or anything if you go a little deeper....the main things are that you need to have good buoyancy control (especially if you have a thick wetsuit or need air in your BCD at depth) and need to pay closer attention to 1) depth 2) air pressure and 3) time. If you're REALLY shallow, you can pretty much dive until you're cold, bored, or the boat crew is banging wrenches on the ladder, the international signal for "get your *** back on the boat, we're late for lunch!" Deeper, nitrogen narcosis & nitrogen loading are things to be aware of. But if you're a competent diver and know enough to pay attention to these things, diving to recreational depths (130', 40m) isn't anything to be "afraid" of. If you're at all concerned (or even if you're not, I suppose...) it's best to gradually work your way down a little deeper, when you have good conditions, etc.

What I do with my customers as a general practice, if we have a dive planned to 100+ feet, is stop for a few minutes at 50 feet or so....watch them, so how they look, and have a pre-arranged "is everybody comfortable with the planned depth or would you rather stay at this depth instead" signal. (that's not in the PADI handbook, so I discuss it with them in advance.) I sort of alter the "plan your dive/dive your plan" rule to "plan your dive/dive your plan or make it easier depending on circumstances."

Anyhow, don't go deeper until you're ready...if you don't "feel" ready, it won't hurt you to wait longer...but don't go into it feeling "afraid" or you're already in trouble.

Chris
(formerly signing in as "iruka" but the message board somehow ate that name, and I'm using "cantlogon" until I can get it back )

 

[ew1usnr]

Boogie711 once bubbled...
that says if you stay above 33 feet, you won't get bent?

Nothing is impossible, but getting bent from a dive above 33-feet would be much less likely than below it.

I've read that for saturation diving, even above 33-feet, something like 20-feet is recommended as the actual no decompression depth. But saturation diving above 33-feet is not a common practice.

If you want to do a safety decompression stop after a dive to 30-feet, go ahead.

 

[ew1usnr]

quote:
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Boogie711 once bubbled...
that says if you stay above 33 feet, you won't get bent?
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Using the US Navy air decompression tables, the standard practice is to round up to the next greater depth. 33 feet would be treated as 40 feet. The decompression categories begin at 40-feet and the no deco limit for 40 feet is 200 minutes (3 hours 20 mins). Using big tanks, or making rapid repetitive dives on single tanks, dives to 33-feet exceeding 200-minutes can put a diver into a decompression status.

Therefore, according to the US Navy tables, down to 30-feet (not 33) is the no decompression zone.

 

[ew1usnr]

ew1usnr once bubbled...
quote: Therefore, according to the US Navy tables, down to 30-feet (not 33) is the no decompression zone.

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I think that it is standard practice to measure depth from chest height. A hard hat diver stands on the bottom. So, even if his feet were at 33-feet, his chest would be at 30. So, that would mean the old hard hat diver was correct after all. A 33-feet bottom would be the limit of where he could work without worrying about decompression (according to the US Navy tables, the best available guidance at that time).

 

[Boogie711]

Don't misunderstand me - I know that diving within the limits of the tables is always a good idea. But diving the tables are no guarantee that you won't get bent.

The likelihood of getting bent after 33 feet is extremely slim, I will be the first to agree. I guess I just had a problem with your blanket statement:

If you want to be completely safe from the bends, it is still a good definition

since you will never be completely safe from the bends, even after diving to 33 feet.

I know a diver who went to 90 feet on 32% for 10 minutes. Did a stop at 45, 30, 20 and then hung at 15 feet for 19 minutes while they loaded the boat... he figured he had gas, he was going to wait on the boat or in the water, so he may as well wait at 15 feet.

Next day he had to go for a ride in a chamber. He even stumped DAN. But undeserved hits do occur. Mind you - circumstances are different, obviously, but - undeserved hits do occur.

 

[ew1usnr]

Boogie711 once bubbled...
Mind you - circumstances are different, obviously, but - undeserved hits do occur.

OK. I shouldn't have used the word "completely". The truth is that there is nothing that you can do as a diver that will provide a 100% guarantee that you will not experience decompression sickness as a result of making a dive. Regardless of depth, regardless of duration, and regardless of decompression stops.

The only way to be completely safe is not to dive. Period.
(But this is an absolute also.)

 

[padiscubapro]

jbd once bubbled...
OW certification is for depths to 60 feet. This is primarily for safety.

Depends on agency..

ANDI's ow is a 100ft/33m cert, AOW is 40m/130

Granted the ANDI OW program is considerably longer than most other programs, but don't generalize...

ANDI teaches the use of an RBS for all of its divers.. This IS for safety....

 

[o2scuba]

I don't think an instructor should ever utter the word "boring" in any regard to diving.

It's gonna be tough to sell that deep diver specialty later if you tell em it's boring down there

I've discussed this issue with other PADI instructors before.
Some other considerations that I've heard and/or thought about:

Gerally speaking, most new divers are inclined to check their air supply more frequently than their time (granted if they are certified, they should be darn diligent at BOTH) but in reality... ?

at 60 ft the NDL is 55min (PADI). Most new divers would reach 500psi long before their NDL (granted this is not consistant, looking at majority here)
Going deeper increases the likelyhood of "the abilty" to pass the NDL before air supply. Even an air-hog could easily do an 80ft dive for over 30min

Consider also bouyancy control. New divers are more likely to accidently go slightly beyond the planned depth (oops, I dropped down to 63ft for a couple of minutes) especially on a wall dive (for example). This makes a significant change in the NDL(especially using the standard RDP).

60ft to 70ft is also one of the bigger "jumps" in the PADI tables.

In the unlikely event that CESA is necessary, 60 feet is a reasonable expectation of sucess for even an inexperienced diver.

Then there's the psychological aspect. Building confidence at a "reasonable" depth.

There has to be some liability issues here as well. We are talking about PADI afterall. They need to make a "standard" that is considered (for lack of a better term) "legally prudent"

 

[String]

Presumably his way of saying "take it easy" and dont rush things.

Statistically you are FAR more likely to have an incident below 30m then above it, also any incident has potential to be more serious at depth. Deep dives also need more planning.

All in all, take your time before doing them.

As for his points though, poor:

1) Not really, although i see no point in diving deep just because its there, there is plenty to see. What if theres a lovely wreck at 140fsw ? Thats something to see. Some nice swimthroughs ? Life ? Basically, this point is wrong

2) "boring" i think refers to (1) which ive already discounted. As for cold - wear proper thermal protection. I dive in a dry suit so it doesnt affect me, yes its oftern coldER below a depth but not "cold". Even that isnt always true, a few weeks ago i had 17c on the surface and 17c at 40m

3) is just back to taking it easy, get some experience before you start planning deeper dives. Although you can get bent shallower than 60ft its far easier to do so with deeper dives, NDLs are smaller, buoyancy is more critical to hold a deco stop and so on.

 

[ew1usnr]

Boogie711 once bubbled...
I know a diver who went to 90 feet on 32% for 10 minutes. Did a stop at 45, 30, 20 and then hung at 15 feet for 19 minutes while they loaded the boat... he figured he had gas, he was going to wait on the boat or in the water, so he may as well wait at 15 feet.

Next day he had to go for a ride in a chamber. He even stumped DAN. But undeserved hits do occur. Mind you - circumstances are different, obviously, but - undeserved hits do occur.

I'm wondering about this. The no deco limit is 30 mins at 90 feet, on air. This guy gets bent after just a 10 minute bottom time? On a nitrox mix? That just doesn't sound right. Had the guy been bent before? It sounds like he was showing caution far beyond the the normal call of duty. Also, the Navy tables are based on a standard steady ascent rate. Could it be possible that he was so slow coming up that he "outsmarted" the tables? Staying in the water longer than necessary extended his total dive time, maybe his residual nitrogen loading, and allowed him to get colder than he would have been otherwise. Maybe if he had just come up after a ten minute bottom time he wouldn't have gotten bent. This is all just speculation and not meant to insult anyone, and I am not unsympathetic to the diver involved.