History of 18m depth limit?

[Storker]

I assumed 18m was selected as it gets you to the surface in 1min at max recommended ascent speed.

I'm pretty certain that 60'/18m was chosen because 60 is a nice, round number somewhere in the vicinity of where you could get into some more serious trouble if you messed up. The closest metric round number is 20m, which is the current limit for e.g. CMAS 1* which happens to be the Euro equivalent to PADI OW. 18m (60') isn't such a round and nice number.

 

[Seaweed Doc]

When I took my open water class in the 80's we had tables to 200'. My instructor gave us cards for PADI, NAUI, YMCA, and we could get a CMAS card for extra. As long as we stayed out of deco, we were good to go. I don't know how you could stay out of deco and hit 200' though. I don't remember exactly, but I seem to think it was 4 minutes at 200'.

My experience was from YMCA in 1985 and was very similar. We used Navy tables, where "60 at 60" was easy to remember, and you could more-or-less add/subtract a minute per foot of depth from there, at least rounded up to 10 foot increments.

However, we were also taught deco tables and the only limit we had was 200' on ordinary compressed air. (We were told things like trimix were beyond us, and I don't recall nitrox discussed at all but it might have been. Wikipedia suggests nitrox training to rec divers began in 1985, and my instructor was old school for sure. We learned in horse-collars, though with power inflators. Drysuits in Puget Sound were for sissies.)

In terms of depth limits, we did a dive to 60' for certification. We were advised to gradually increase the diving depth we were comfortable with, keeping in mind ox tox at 2.0 atmospheres (not 1.4, as today) and awareness of the effects of narcosis. But if we on our own dove regularly, increased depths by maybe 10-20' at a time, and minded the effect of narcosis, the only ultimate limit was 200'. And the gradual increases were a "recommendation" not a "rule."

Compared to a current class, I'd say we did a lot more in-class and in-pool work. But only 4 openwater dives. I think we probably got a better theoretical understanding of the issues (at least as was known at the time) and more practice on things like buddy breathing. Since it was YMCA and not tied to a shop, there was no effort to get us to overcome substantial anxiety issues. "Diving isn't for everybody, and if it's not for you that's OK" was the mantra.

 

[NAM001]

My experience was from YMCA in 1985 and was very similar. We used Navy tables, where "60 at 60" was easy to remember, and you could more-or-less add/subtract a minute per foot of depth from there, at least rounded up to 10 foot increments.

However, we were also taught deco tables and the only limit we had was 200' on ordinary compressed air. (We were told things like trimix were beyond us, and I don't recall nitrox discussed at all but it might have been. Wikipedia suggests nitrox training to rec divers began in 1985, and my instructor was old school for sure. We learned in horse-collars, though with power inflators. Drysuits in Puget Sound were for sissies.)

In terms of depth limits, we did a dive to 60' for certification. We were advised to gradually increase the diving depth we were comfortable with, keeping in mind ox tox at 2.0 atmospheres (not 1.4, as today) and awareness of the effects of narcosis. But if we on our own dove regularly, increased depths by maybe 10-20' at a time, and minded the effect of narcosis, the only ultimate limit was 200'. And the gradual increases were a "recommendation" not a "rule."

Compared to a current class, I'd say we did a lot more in-class and in-pool work. But only 4 openwater dives. I think we probably got a better theoretical understanding of the issues (at least as was known at the time) and more practice on things like buddy breathing. Since it was YMCA and not tied to a shop, there was no effort to get us to overcome substantial anxiety issues. "Diving isn't for everybody, and if it's not for you that's OK" was the mantra.

sounds very much like my 1968 class with ymca.

 

[Bob DBF]

Initially, and now to a certain degree, recreational scuba diving was for NDL diving. My initial training was for NDL diving, which on the tables at the time maxed NDL at 190', 200' was in deco.

Now the instructors were clear in their training that it was not a good idea to start diving that depth initially, but get experience at shallower depth as mistakes and casualties are easier to deal with when shallower. This was brought home using a j-valve when the air ran out, more so with a k-valve, an unexpected LOA or OOA to mark the end of every dive will catch your attention. As time goes on one learned to head up before that happens, using an SPG solved the issue.

I believe that the 60' recommended limit "rule" is a train by catchphrase shortcut instead of the longer discussions on how one extends their limits safely that I received. I guess it works, but gives little insight into extending ones skills and limits without another class.

There was no 60' limit in '62 when I started, it is mentioned as a recommended limit in the 1980 PADI OW manual. I don't have any earlier agency manuals so I don't know when they started using that recommendation.


Bob

 

[hroark2112]

60' is not a limit, it is a recommendation.

 

[broncobowsher]

I just found an old PADI set of tables. Various copyright dates from '86 til '94. Shows to 140 feet but a gray area below 100' and at the end of the NDL stating a safety stop is required.

So in the mid 90's 140' was still acceptable for the Open Water class. Falls in line with my NAUI training in '91.

I want to say early 2000's was probably the 100'
Still not sure when the 60' rule/recommendation was implemented. I am thinking late '00s? Don't have the books/paperwork from this era to check.

 

[Protondecay123]

I just found an old PADI set of tables. Various copyright dates from '86 til '94. Shows to 140 feet but a gray area below 100' and at the end of the NDL stating a safety stop is required.

So in the mid 90's 140' was still acceptable for the Open Water class. Falls in line with my NAUI training in '91.

I want to say early 2000's was probably the 100'
Still not sure when the 60' rule/recommendation was implemented. I am thinking late '00s? Don't have the books/paperwork from this era to check.

I'm certain that on our last PADI OW qualification dive in Gitmo in 1989, we went to 100 feet along the wall there. We stayed under our Deco time, But Our DI wanted us to get the experience.

 

[Dzydvl33]

More courses = More money
" "Limits" " = less liability.
That's my thoughts on it.

 

[tursiops]

More courses = More money
" "Limits" " = less liability.
That's my thoughts on it.

What a bleak view of life.

 

[Dzydvl33]

What a bleak view of life.

Bleak??? Why?

I was speaking from the certifying agency's view.