Dive Tables vs. Computer Algos - repetitive rec dives

[Rred]

The original USN tables were "warm water tables". This was very specifically confirmed to me by a USN Chief Diving Medical Officer at the first Beneath the Sea conference. He also referred to cold water tables (and since this was pre-internet I certainly wasn't going to a "Naval library" to chase those) and to bumping up either one or two groups for those of us who dove in cold water (defined as cold enough to require any type of wetsuit) with the base tables.

But looking through my old files, I see the USN's "new" tables went from 60/60 to 60/50 (ft./min) by 2006, while the NOAA tables still showed 60/60. And some notes that the 60/50 time reduction was the result of microbubble data that had been collected by then.

I'm not a "PADIte" so I never paid much attention to PADI tables, but I recall that PADI somewhere along the years had also either acknowledged "cold water" or bumped their printed cards to be more conservative.

There's no reason that all the tables really have to agree. Or all the computers. There is always the assumption that a dive plan will be "safe" for a significant number of the intended users--and that some will be bent even when following it. For the USN, the question is "How many ultra fit 21 year old boys can we send out and mainly get them back again?" For NOAA it might be "How many contractors will we have to replace?" and for PADI it might be "When do the news articles start to discourage customers?"

All valid reasons to declare different "safe" profiles. There's just no medical knowledge of what "absolutely safe" is, or how to adjust that for the individual diver. The USN and NOAA will share their reasoning and the numbers behind it. The dive organizations may not, because of liability concerns. The computer makers..."trade secret".

 

[tursiops]

For the USN, the question is "How many ultra fit 21 year old boys can we send out and mainly get them back again?" For NOAA it might be "How many contractors will we have to replace?" and for PADI it might be "When do the news articles start to discourage customers?"

This is on the fine line between silly and slanderous, and is certainly mean-spirited. By the way, NOAA divers are usually employees and only rarely (if at all) contractors. Get your facts right....

 

[boulderjohn]

I'm not a "PADIte" so I never paid much attention to PADI tables, but I recall that PADI somewhere along the years had also either acknowledged "cold water" or bumped their printed cards to be more conservative.

The PADI tables tell you that when diving in cold water, plan the dives for 10 feet deeper than they actually are.

So what constitutes cold water? I tell my students that the primary reason for it is the effect of the cold on blood circulation, so whether it is cold enough to merit special consideration or not depends as much on thermal protection as on the actual temperature of the water. When I dived in Hawai'i the first time, the water was a lot colder than I expected, and I felt cold until I got more wetsuit on my body. When I dived in Puget Sound, I brought a drysuit and my warmest undergarments--which was complete overkill. I was sweating at the end of a one hour dive.

 

[dmaziuk]

This is on the fine line between silly and slanderous, and is certainly mean-spirited.

With a male chauvinist on top. It should be: "How many ultra fit 21 year old boys and girls can we send out and mainly get them back again?"

 

[Rred]

Tursiops, pick nit all you like, but I was told the USN criteria by a former frogman, as in an original WW2 D-day scout, and the Navy has been blunt about it over the years. Their business is combat, and in combat you can and do accept losses that a recreational business never can or should.

John-
Thanks for clearing up the current PADI cold water adjustment. Do you have any idea around when they first started conceding that there SHOULD be a cold water adjustment?

 

[boulderjohn]

John-
Thanks for clearing up the current PADI cold water adjustment. Do you have any idea around when they first started conceding that there SHOULD be a cold water adjustment?

No idea. It was that way when I was certified a couple decades ago.

 

[shurite7]

Thanks for clearing up the current PADI cold water adjustment. Do you have any idea around when they first started conceding that there SHOULD be a cold water adjustment?

This procedure has been around since the mid-1990s. NAUI has a similar procedure for cold water. Instead of planning the dive to 10 feet deeper, a diver is to plan the dive at the next greater time. The outcome is similar in the sense it makes the dive more conservative by reducing the allowable dive time.