Is the Deep cert really necessary?

[Blackcrusader]

del

 

[Blackcrusader]

I was just in the Caymans, and I did not see this. Our dive operator on Grand Cayman asked to see a nitrox card, and they very pointedly did not want to see any other certification card. They did not know our certification levels, and we all did dives to about 100 feet on most days. On little Cayman, the first dives were usually to around 100 feet, and everyone did those dives. The second dives had to be above 60 feet, and they were very strict about that, but it had nothing to do with certification levels.

OK so first dive on 32% max 30m then second dive max 20m? Certainly they are keeping divers safe as even from first dive you can push the NDL limits. Was there a third dive?

 

[boulderjohn]

OK so first dive on 32% max 30m then second dive max 20m? Certainly they are keeping divers safe as even from first dive you can push the NDL limits. Was there a third dive?

You are missing the context of my post. I was responding to a post that cited strict laws for diving governing all Cayman operators, and I was responding that I had just dived in the Caymans with an operator who did not follow such laws.

 

[tursiops]

PADI's Recreational Dive Limit is 40 metres. WHY?

Beyond 40m you greatly increase the changes of running out of gas and experiencing narcosis. Mitigating those things is beyond basic training, and involves extra equipment, decompression, and mixed gases.

From Post#10 in this thread:

The AOW Manual from the same period (Vol 1, 1991) has a discussion on p55 on "deep diving," which it says begins at 60 ft, continues to 110 ft as the "optimal maximum recreational depth limit" and then goes to 130 ft as the "absolute maximum recreational depth limit."

The earliest reference I have on this is Owen Lee's "The Complete Illustrated Guide to Snorkel and Deep Diving" from 1963 (predating PADI and 31 years before the publication of the RDP). Owen was one of Cousteau's divers, and ended his career as an oceanographer at the Naval Lab at Point Loma CA. Chapter 11 includes a discussion of no-decompression depth limits. He points out that above 130 ft is where the most interesting stuff is, and that below 110 ft your single-tank air supply begins to be insufficient and you are risking narcosis.

From Post #87 in this thread:

Apologies in advance for answering a question with more questions but if you answer these for yourself, you will have a better understanding of the recommended limits.

What is the NDL at 130'?
What is min gas at 130' to get two divers back to the surface?
What is the PSI / BAR in the standard aluminum 80 for the above question?
How narc'd are you at 130'?
What is the gas density at 130' and why should you be concerned?

None of the above is meant to be flippant. I, or we, could answer them for you but there is a lot of value in answering them for yourself.

Ignore most of what Blackcrusader says in this thread; he is living in a different world and is usually way off topic.

 

[steinbil]

The deeper you go the more you need luck!

It doesn't matter how skilled you think you are, or how much experience you have, if you run out of luck then all bets are off.... I've known some unlucky people.

Agreed. Luck always plays a part. But you can do a lot to mitigate the effect of bad luck and to increase your chances of being lucky...

One of the things that the PADI deep cert does provide is some experience doing an extended emergency decompression stop while sharing air. Outside of technical diving courses, I am not aware of any other courses that give the diver that sort experience.

GUE teaches blue water ascents with an SMB, while sharing gas and doing stops every 3m - in their OW class(!), and also in their Fundamentals class, neither of which are technical courses.

 

[cousindna]

a. Absolute maximum is 40 metres/130 feet. Exception: TecRec courses as specified in course instructor guide.

OWSI: 18m/60 ft AOW: 30m/100 fi Deep Diver: 40m/130ft

Why is 40m PADI's absolute maximum?

Thank you to those who have made an effort to answer this question and provided significant rational.

A hint: what is the maximum depth that you can DECO on 100% O2 and why?

 

[johndiver999]

[QUOTE="steinbil, post: 10312839, member: 534163


GUE teaches blue water ascents with an SMB, while sharing gas and doing stops every 3m - in their OW class(!), and also in their Fundamentals class, neither of which are technical courses.
[/QUOTE]
When you think about it, to do otherwise is kinda ridiculous.

 

[boulderjohn]

That you to those who have made an effort to answer this question and provided significant rational.

A hint: what is the maximum depth that you can DECO on 100% O2 and why?

It looks to me as if you have a personal answer that you have come up with on your own and are asking us to guess what is in your head instead of referring to references. I won't play that game.

As for your oxygen question, the standard answer is 20 feet (rounded off), because the PPO2 at that depth (1.6) is considered to be the maximum safe partial pressure for decompression stops.

 

[steinbil]

A hint: what is the maximum depth that you can DECO on 100% O2 and why?

You imply that the ppO2 is the leading parameter for a 40m limit. I don't think that is the case. Air has a ppO2 of 1.05, which is quite conservative. As @lostsheep alluded to, gas density is a much bigger concern. As are NDL limits, gas requirements and possibility of an OOG ascent.

 

[tursiops]

That you to those who have made an effort to answer this question and provided significant rational.

A hint: what is the maximum depth that you can DECO on 100% O2 and why?

It sounds like you are confused about O2 toxicity limits for 32% Nitrox, and 40m as a recreational maximum depth.