Diver Training: How much is enough?

[Diver0001]

To me they are a planning/perception tool. My computer is a diving tool.

This is exactly why I'm still teaching both in the OW course. I don't believe we should be diving with tables anno 2013 but I find them handy as a tool for teaching certain concepts. The key is that we need to keep focused on teaching the underlying concepts related to the tables (ie, the "what") and avoid putting too much emphasis on the HOW. The "how" is an historical curiosity, but the "what" is rather important.

Regarding "perception": I've seen a fair number of students who could plan a dive just fine using the tables but had no clue whatsoever about decompression theory.

One such example was a young man (I think he was 13) who I took over from another instructor to do his module 5 theory and the final test. While running through the knowledge reviews I noticed that he was doing the table questions in a way that could only be described as mechanically... so I gave him a few scenarios that were not in the book and at every step asked him "why".

For example,
"what is the NDL at 18 metres"?
He would say "56 minutes".
"why is that important"?
"you can't dive longer than that"
"why not?"
"I don't know."

"What group are you after a dive for X number of minutes at Y depth"
"R"
"and after a 3 hour surface interval"?
"A"
"And what goes on during the surface interval?"
"You go from R to A"
"And what is happening in your body during that time? "
"I don't know"

etc. etc.

And every time I probed under the mechanical way he was doing it, he hit a wall and had no clue whatsoever WHY any of what he was doing was important, other than that the instructor told him he had to.

So I declined to give him the test and sent him home with a list of questions that he had to answer before the next lesson and then got the shop to book another theory lesson for him. His mother was HACKED because I didn't give him the test and his other instructor didn't understand what my problem was. He said, "could he have answered the questions on the exam correctly"? I confirmed that I thought he could. .... "then that's all you need to do".

The point of this post being, without boring you too much, is that

(a) teaching tables does not mean that someone learns anything much about deco theory
(b) teaching deco theory *can* be done using the tables as one tool to transfer *some* of that knowledge, but understanding deco theory is more important than understanding the tables, especially since everyone is now using computers.

R..

 

[boulderjohn]

Wayne,
If you log the dives and all of those dives are multi-level dives (because that's just how a computer works) then within a few dives you'll be off the tables in terms of bottom times vs. depths (ie, you'll be beyond "Z" in terms of what the table can handle in terms of input). Logging simply isn't enough.

A number of years ago I did a dive to 100 feet to look at some garden eels. Once I had taken in that sight, I ascended pretty far up the reef to continue the dive. After a while I found myself drifting along at the top of the reef, where there was a lot of good stuff to look at. I finished the dive after a total of 80 minutes. If I had been using the PADI tables, I would have been limited to 20 minutes of bottom time on that dive. If I had been using the U.S. Navy tables, it would have been a little more--I don't have them with me at the moment. I ended the dive because I was low on air--according to my computer, I had plenty of no deco time left. If my computer had had gone bad at the end of that dive, and if I did not have a backup, getting on the tables would be problematic--just a wild guess.

---------- Post added January 14th, 2013 at 09:27 AM ----------

When instructing an OW class session, I do an introduction to decompression theory at the same time that I go over Boyle's Law. In the PADI system, taht is question #5 of the first learning module. (I actually am adding both Dalton's Law and Henry's Law in, but there is no need to use those terms.) In that context, it makes sense to them why nitrogen diffuses into the body at depth, and it makes sense to them why it comes out as you ascend. IT makes sense to them why you have to ascend at a slow rate, etc. They understand all they need to know.

In the current PADI system, students can choose to take the course with tables or with computers. It makes no difference to me at this point in the class. I have taught them about decompression theory.

When we reach the 4th learning module, we start talking about how to plan for decompression. If the students are taking the table version, we talk about how we use the tables to plan decompression. They can see it. If they are learning the computer, we use a really neat animated program that they can download. It shows how nitrogen loading changes by depth, and it shows how a generic computer deals with it. They can see it in single dive mode, multiple dive mode, multi-level dives, etc. It is extremely complete.

 

[Peter Guy]

"Measuring with a micrometer, marking with chalk and cutting with an ax." (author forgotten)

This whole "if you lose your computer" argument is just so over the top. We all know that "the tables" don't work well for multi-level dives although there are some work-arounds if absolutely needed. For example, one can use, not your max depth, but your average depth as the bottom depth. Or one can use a "no surface interval" time for computing a multi-level dive and tread a multi-level dive as several dives without surface intervals.

Yes, this is NOT the recommended strategy and isn't been (?) tested -- but given the inherent conservatism of "the tables" I'd certainly be willing to dive "conservatively" based on those strategies if my only computer died in the middle of a vacation. (And assuming I still had not only a bottom time, and yes, I do have a Rolex!, but also a depth gauge -- and I haven't used a non-electronic depth gauge in, lordy, 40 years? Hmmm, can you still get non-electronic depth gauges new?)

DCBC -- while I'm sure you and all the other commercial divers, don't use "computers" during your saturation dives, I'd be shocked to learn that your handlers/specialists didn't use computers to generate and track your dives and decompression. My guess (and it is only a guess) is that your "We don't use no stinkin' computers" is akin to the macho "techincal diver" that inputs his dive plan into V-planner on his laptop, prints out his deco schedule using a laser printer and waterproof paper, and keeps his time and depth by looking at his electronic bottom timer. Nope, he's just using the "computer between his ears" for his deco obligation. You won't catch him using any of this fancy/smancy electronic stuff!

 

[DCBC]

DCBC -- while I'm sure you and all the other commercial divers, don't use "computers" during your saturation dives, I'd be shocked to learn that your handlers/specialists didn't use computers to generate and track your dives and decompression. My guess (and it is only a guess) is that your "We don't use no stinkin' computers" is akin to the macho "techincal diver" that inputs his dive plan into V-planner on his laptop, prints out his deco schedule using a laser printer and waterproof paper, and keeps his time and depth by looking at his electronic bottom timer. Nope, he's just using the "computer between his ears" for his deco obligation. You won't catch him using any of this fancy/smancy electronic stuff!

Peter, another misquote and fabrication of what you think I said, but didn't. I personally carry two dive computers when I dive deep for recreational purposes. Commercially however, tables are used that are often based on propitiatory algorithms. One such algorithm, the Variable Permeability Model (VPM), was created by David Yount and Don Hoffman (researchers at the University of Hawaii) in 1979 and was later revised by Erik Baker using Fortran for calculation of the tables in 1986. It was quickly adopted by some Commercial Diving companies and often refined. This wasn't the first time an unconventional algorithm was adopted by the industry, as in 1966, Brian Hill's thesis entitled 'A Thermodynamic and Kinetic Approach to Decompression Sickness' gained a following and further development was underway. DCIEM had completed an iteration of it's tables, largely with the assistance of slide rules (and who knowns, perhaps an abacus). ...Either way, as a 'computer' may be defined as 'A person who makes calculations,' all tables were created with a computer one way or another.

To eliminate misunderstanding, I support the use of decompression computers and was involved in their development at DCIEM. I also use a GPS in my vehicle, but that doesn't mean that I don't think it a valuable skill to know how to read a map...

 

[ElGaucho]

I am a macho Tech diver that uses no stinking electronics whatsoever,

This message was verbally dictated to a midget who travelled to Scubaboard servers and punch card fed this reply.

 

[Diver0001]

I don't think that's really what he way saying, but your response made me think of this:



R..

 

[Martigan]

To eliminate misunderstanding, I support the use of decompression computers and was involved in their development at DCIEM. I also use a GPS in my vehicle, but that doesn't mean that I don't think it a valuable skill to know how to read a map...

I love this analogy, because I think it is a very apt one. Many people nowadays tends to rely very heavily on technology and do not take the time and effort to understand the phenomenon behind it. More and more people don't know how to use a map, and don't own even one of the area they are travelling into. They use their phone, or a dedicated GPS device. Problem is, they tend to fail, and suddenly they don't have anything anymore and are completely lost...
To be honest, GPS devices are failing more than dive computers, but still, this is an issue not to be able to understand cartography and planar representation of space.

 

[DCBC]

Although we really didn't come-up with a definitive answer my OP, it was good to hear everyone's input. Regardless of the difference of the opinions presented, clearly diver training is something that can affect us all. It's in our interests to assess the direction diving is taking and do what we can to protect our sport.

In 1958, the Ontario Underwater Council was formed to advocate safe diving and form a liaison between Divers and Government. At that time, the Government was considering diver certification legislation and had passed a law against spearfishing. The OUC established Diver Training Standards and were recognized as the voice of SCUBA Diving in the Province of Ontario. The organization is a non-profit, made up of the various Diving Clubs in the Province. It's grown quite a bit from the 300 divers it represented in 1958.

I'd be interested in knowing about similar organizations in your area. Who advocates safe diving for you? Clearly 'for-profit organizations' often act in their own self-interest and this may not always reflect the best interests of the individual.

 

[The Chairman]

Who advocates safe diving for you?

ScubaBoard. Sure, I'm biased, but there is no other organization that has come close to reaching the number of divers we have, even to enticing agencies to look, perchance to change.

 

[Martigan]

Who advocates safe diving for you? Clearly 'for-profit organizations' often act in their own self-interest and this may not always reflect the best interests of the individual.

In France, diving within a club or a dive shop is regulated by the Ministry of Sports, through the "Code du Sport" (Sport's Code, section relative to diving...).

In order to be able to be a professional teacher in France (i.e. earn money from your teachings), you have to possess a national level of instruction, and there is a clear definition of the courses content for the levels of instruction.

In order to be a non-professional teacher, you have also to follow some steps, but there are different ways of reaching them depending on the federation you are affiliated to, either the FFESSM (who has an official delegation from the ministry to set up course content for each level), and the FSGT, which is an alternative federation, that refers to the same levels of instruction, but that has a different way of approaching pedagogics.
There are also independent instructors autorized to acts within this frame, but they are few and between in the grand scheme of things.

But I would say that on the practical side of things, the two main players advocating "safe diving" are the two federations (FFESSM and FSGT).