Diver Training: How much is enough?

[DCBC]

I have nothing against the tables but they have become antiquated due to the advent of reliable, low-cost computers and should be retired.

Not surprisingly, I disagree. The tables are applicable to every SCUBA Diver's 'need to know.' Computers are man-made devices that are subject to failure. Batteries run dry, the system can flood and failure occurs. I don't believe it's in the best interests of the Student to support the attitude that knowledge of the tables isn't required if a diving computer is being used. Much of diver training surrounds prevention/action during equipment failure (visual/hydrostatic inspections, regulator maintenance, back-up lights, procedures during regulator icing, etc.) Every device made by man will fail. What we don't know is when...

---------- Post added January 13th, 2013 at 09:31 AM ----------

Actually Wayne, since we're on the topic of yo-yo diving (or zig-zag profiles), do you have any recollection regarding how the advice to avoid those things got raised to the status of "best practice"?

I believe that if you teach the tables, you also teach the Authorities rules in how to apply them. Any dive (or subsequent dive) is considered to be the same dive unless the Surface Interval is more than 10 minutes (15 for some tables) between the dives. In my mind, this is best practice. To say anything that conflicts with this isn't.

I don't believe multiple ascents has ever been considered to be against 'best practice.' One study that gained some ground was undertaken at the University of Queensland. The Researchers felt that multiple ascents were a 'risk factor' largely due to the speed of most ascents. To lower this risk, it was felt that it would be beneficial to include multiple ascents as a risk factor. Studies do however support the much greater factors: poor fitness, overweight, intense cold water and physical exertion during and/or after the dive. It is recognized to be a larger factor for recreational decompression diving (although it's disregarded in the commercial sector). Certainly it's not a factor when considering a recommended 60 or 70 foot depth limit.

The evidence available has not caused the USN, DCIEM, NAUI or PADI (to my knowledge) to change it's "rules for using the tables." Multiple ascents are still considered allowed as long as the rules are followed.

 

[Diver0001]

Not surprisingly, I disagree.

Fully expected.

The tables are applicable to every SCUBA Diver's 'need to know.'

Understanding on/off gassing, decompression models and decompression sickness is a "need to know". Lots of instructors use tables as a vehicle by which to address those things but my thinking is that the relevant theory can be taught in other ways as well; perhaps even in ways that are more effective and to the point. Many instructors confuse "teaching tables" with teaching deco theory.

Computers are man-made devices that are subject to failure. Batteries run dry, the system can flood and failure occurs. I don't believe it's in the best interests of the Student to support the attitude that knowledge of the tables isn't required if a diving computer is being used.

An attitude that one does not need to know deco theory would be wrong, but as I pointed out before, teaching tables does not equal teaching deco theory. If one has a good knowledge of the theory then diving with a computer is completely reasonable and completely safe way to approach it.

As for failures. This is a common argument but computer failure are rare and if the computer craps out the dive is over. Moreover, it's impossible to fall back from a computer to the tables on the fly anyway so the whole point about "if the computer dies" is moot from the perspective of being able to carry on with the dive.

That said, I know computer failures do happen. During my last 800 or so dives I've had 2 computer failures, one of which could have been avoided if I had been paying better attention to the battery indicator. Of all of the dives I've done with a bottom timer, I've also had one bottom timer crap out. It was an old-fashioned "wind up" one that activated under water once the pressure built up. You would have liked it, but it flooded, just like a computer can. The point here being that a bottom timer, even the good-old-fashioned ones can flood and a computer can flood. In terms of your dive, the response is the same. Dive over, ascend and get it fixed.

Much of diver training surrounds prevention/action during equipment failure (visual/hydrostatic inspections, regulator maintenance, back-up lights, procedures during regulator icing, etc.) Every device made by man will fail. What we don't know is when...

If it's a big issue, then redundancy is key. If, for some reason, you're making a dive whereby aborting in response to a broken computer is not an option then you simple take two. The vast majority of divers never get in that situation.

R..

 

[DCBC]

It was an old-fashioned "wind up" one that activated under water once the pressure built up. You would have liked it...

LOL I haven't used a BT in 30 years, but admit to still using the bezel on my watch....

 

[billt4sf]

One of the best divers I've ever met told me that a card is simply a certification that you are ready to begin learning. .

This is what I say (but I am not that "one of the best divers ever" diver).

Unfortunately most dive classes like OW (and typical vacation boat dives) do not teach how to be a good buddy. It's all about "follow me".

- Bill

 

[RTee]

I have nothing against the tables but they have become antiquated due to the advent of reliable, low-cost computers and should be retired. The use of a computer, and learning how to plan and dive with a computer, should be required and tables should be optional.

Diver0001, not to head into a rabbit hole (as this one as also been the subject of many threads) but I will have to disagree with you on this one. However, what you do mention is the perfect approach if all you want to do is to develop generations of divers with unnecessary overdependance on a piece of kit resulting on an initial reflex of thumbing the dive (no matter what???) and pick lint out of their belly button for the next 12 to 24 hours, even when the dive (and subsequent dives) could still be safely conducted and planned (depending on profile being followed or adopted in light of) or creating an absolute requirement to purchase an additional low cost (low cost relative to what...certainly not to dive tables) DC to be used and carried as a back-up.

 

[Diver0001]

Diver0001, not to head into a rabbit hole (as this one as also been the subject of many threads) but I will have to disagree with you on this one. However, what you do mention is the perfect approach if all you want to do is to develop generations of divers with unnecessary overdependance on a piece of kit resulting on an initial reflex of thumbing the dive (no matter what???) and pick lint out of their belly button for the next 12 to 24 hours, even when the dive (and subsequent dives) could still be safely conducted and planned (depending on profile being followed or adopted in light of) or creating an absolute requirement to purchase an additional low cost (low cost relative to what...certainly not to dive tables) DC to be used and carried as a back-up.

Well... I'm sure if you search/replace "BCD" or "SPG" where you wrote "tables" then you'll have an argument that was waged when the last major paradigm shifts happened in diving.

Every single innovation is resisted in this sport, by some more than others. Personally, I'm not operating on that frequency. I would have been an early adopter of the BCD, the octopus, or the spg, just as I was an early adopter of the long-hose and spring straps. If my spg broke, I would end the dive. If my BCD broke, I would end the dive. The last time my computer broke (which was about 6 weeks ago) I ended the dive (albeit doing all necessary stops along the way based on back-up meters). I don't feel "overdependent" on my spg, or my BCD, or my computer for that matter. They are tools that I use to dive safely. If something is wrong with them, I don't keep diving.

Secondly, if we do or do not teach dive tables will not affect which divers decide (or are motivated) to improve, think and develop, and which ones aren't. Teh most motivated divers will find tables useful. Most will not. Most will not need them, or want them, just as I would never again want to dive with a tank that has a J-valve instead of an SPG.

R..

---------- Post added January 13th, 2013 at 07:17 PM ----------

but you're right, it's a rabbit hole and those who aren't making the paradigm shift aren't going to budge an inch at this point. It will take time.

 

[dumpsterDiver]

Diver0001, not to head into a rabbit hole (as this one as also been the subject of many threads) but I will have to disagree with you on this one. However, what you do mention is the perfect approach if all you want to do is to develop generations of divers with unnecessary overdependance on a piece of kit resulting on an initial reflex of thumbing the dive (no matter what???) and pick lint out of their belly button for the next 12 to 24 hours, even when the dive (and subsequent dives) could still be safely conducted and planned (depending on profile being followed or adopted in light of) or creating an absolute requirement to purchase an additional low cost (low cost relative to what...certainly not to dive tables) DC to be used and carried as a back-up.

 

[Diver0001]

even when the dive (and subsequent dives) could still be safely conducted and planned (depending on profile being followed or adopted in light of)

I just want to revisit this for a second and ask you a question, not to turn the tables but as a matter of curiosity.

Suppose a diver on vacation has been diving for 3 straight days doing 4 dives a day and then suddenly the computer craps out. What would be your strategy for "falling back" to tables?

I mean... you're off the charts, aren't you? Wouldn't you have to do the same thing that the computer diver would have to do? Sit out for 24 hours so you that you got yourself back into a known starting point for recommencing diving?

Moreover, if your diver did fall back to tables, skipping day 4 of, say, 6 days of diving, then falling back to tables would mean that in day 5 and 6 they would have significantly shorter bottom times (or significant constraints on their flexibility with respect to depths) as compared to the diver who waited for 24 hours and got his/her computer fixed (or arranged to rent a new one). So all in all, in my way of seeing things, it would be the diver who fell back on tables that would spend more time "staring at their belly button" in comparison to the computer diver, for this reason. Don't forget, one of the big reasons computers are so popular is that they turn every dive into a multi-level dive and give you longer bottom times as compared to tables.

Consider another scenario where someone is doing 1 or 2 dives on a dive day and then not diving for another week (say, typical local diving). Here we have two divers, one with a computer and one who insists on using a bottom timer and tables. Both are using instruments that can fail but both instruments are very reliable and maybe fail once in that 10 year time frame. As I mentioned above, it doesn't matter if it's a bottom timer or a computer, they can both fail. So both divers will *probably* miss statistically the same number of dives over the years, but which one will, in that 10 year period of time between failures, spend more time in the water? The one with the computer, or the one with bottom timer?

I know it's seductive to see eliminating tables as some form of "dumbing down" but in reality adopting the computer is more a case of smartening up.

As for the cost of it... meh. Bottom timers cost about 100 euros. A basic computer costs about 200. It's not like it was years ago when only rich-kids could afford a computer. If you can afford to dive you can afford a computer. The big-ass additional expense we're talking about is round-about 100 Euros. That's a price that most people don't even bat an eye about anymore, especially given how much more time in the water you will get when you use a computer to dive.

In those very rare cases where someone can afford to dive but can't afford the extra 100 euros for a computer, then there's nothing stopping them from learning tables..... I just don't see the point in making *everyone* learn it to accommodate this minuscule group who may not have a choice.

R..

 

[boulderjohn]

Random thoughts on some of the most recent twists in this thread....

1. I always dive with a dive watch in pool instruction. I have several relatively expensive dive watches. On two different occasions, at the end of the pool session I saw that the watch had somehow lost time--10 minutes one time and 20 minutes the other. The actual time of day was later than my watch indicated, and my watch had been correct when I started the sessions. I have never had a computer fail, but I understand that when they do, you look at them and don't see anything. You then end the dive. That sounds a lot better than what would have happened if I had been relying on my watch bezel to guide a table-planned dive rather than doing skills in a pool when my watch failed. If such a dive had been to any appreciable depth, I probably would have been bent, because I would have thought my bottom time was much shorter than it actually was.

2. Mark Powell wrote an excellent book, Deco for Divers, which will tell you anything you could want to know about decompression theory. Bruce Weinke's Technical Diving in Depth tells you much more than you would ever want to know about decompression theory, assuming you have the calculus skills to understand it. Neither book tells you how to use tables. Decompression theory explains why we have to dive within certain limits and follow ascent profiles. The actual limits and ascent profiles you use is another matter altogether. You can do it with tables, or you can do it with computers.

3. I have done a lot of diving, especially decompression diving, without the use of computers. For most of my training, computers were absolutely not allowed, unless they were in gauge mode. They were regarded by my agency as the spawn of Satan. One of my friends was using his computer in gauge mode for a dive for that reason. He and has buddy had been taught, as I was when training with them, that computers could not be trusted, that they should rely upon the computers between their ears instead. They were taught to estimate average depth and plan their ascent accordingly. They were taught to ascend at a specific ascent rate until their first deep stop and then follow their table-planned ascent profile. Because he had a computer in gauge mode, he was able to download a profile of the dive, which showed that they were mistaken in their estimation of their average depth--either their mental math was off or they had not noticed the times they had dipped down below their planned depth for a while. The profile also showed that they had taken much, much longer to ascend to their first deep stop than they were supposed to. They had not noticed either of those issues, which is probably why they got bent. The computer noticed it, though, and it would have adjusted its ascent profile accordingly if it had not been in gauge mode.

 

[The Chairman]

The evidence available has not caused the USN, DCIEM, NAUI or PADI (to my knowledge) to change it's "rules for using the tables."

False, the maximum ascent rates have been decreased from 60 t0 30FPM. As for yo yo diving messing you up, just read BoulderJohn's post.

I don't promote yo-yo or bounce diving. You are the only instructor I know who does and without any support for the practice.