Are dive computers making bad divers?

[boulderjohn]

However, just because some of them now have a computer strapped to their wrist, that does not mean they have stopped properly planning their dives. In the DIR mindset, you have your dive well planned before you get in the water. Part of that planning includes having a set of tables that are cut for the planned depth and time, plus a few contingency depths/times, and you should also understand how the tables are formulated so that in the event that your dive drastically deviates from the plan, you can adjust them as needed. In true DIR fashion, you should have a pretty solid understanding of how long your dive will be before you ever get wet.

I don't know any training agency that does not advocate the same thing. Technical divers who have never heard of DIR (and, believe it or not, there are many) have the same mindset.

I teach technical diving for two agencies. Both teach creating a thorough dive plan before entering the water. Both teach creating a pre-designed profile and contingencies before you get in the water. When I do deco diving from a boat during my winters in South Florida, before we hit the water the boat crew goes around the deck asking each team what their planned run time is. Now, I don't know what training each team has, but every one of them has obviously planned the dive ahead, and it sure looks to me as if just about every one of them is carrying a computer. The shop I usually use for these dives is GUE-affiliated.

How the dives differ, I imagine, is in what happens under water. If you have a pre-planned strategy, written contingencies, and a computer that is programmed to give the same plan, how to you use all of that? Some people follow the plan strictly, using the computer only if something forces them far enough away from those plans that they prefer to follow the computer. Others follow the computer, planning to use the written plans (with their backup gauges) only if the computer fails. I think the trend in my personal observations is to the latter, especially since people tend to plan to the worst case scenarios and are likely to have done a shallower dive than their written plans called for.

---------- Post added December 8th, 2015 at 11:37 AM ----------

I don't see how you can learn to plan dives and internalize an understanding of the relationships among depth, no-stop time, and surface intervals without tables. If I only had a computer I'd run a bunch of scenarios, write down the results, and make tables. I don't see how anyone can make an informed choice on whether it's worth pursuing Nitrox certification, or using Nitrox for any one particular dive, without tables or, again, running a bunch of scenarios on a computer and making up some tables. Same thing applies to deco dives and accelerated decompression.

With deco dives, this may be a terminology issue.

Technical dives have so many variables that if you had a paper table, it would be book length. Take a look at the full navy air tables and see how many pages they run. Now imagine it with all the varieties of nitrox and trimx being used. It would be unusable. Desktop software puts all of that into a program. You put in your planned depths, times, and breathing gases, and they spit out that portion of that book-length table that applies to you. They are tables--they just don't look like it.

So when someone is planning a deco dive, he or she will put in the planned numbers and see what it says. Typically then, the diver will do the same thing for a dive 5 feet deeper and a dive 5 minutes longer. They will see what it says. All three plans will be written down. As kensuf said, you don't have to do that too many times before you begin to get the gist of things. Do enough dives of roughly the same depth and time, and you almost have it memorized.

The same is roughly true of recreational diving. You don't have to come up from too many 70-90 foot dives with lots of air left in your tank to start thinking about the benefits of nitrox.

 

[drrich2]

I don't see how you can learn to plan dives and internalize an understanding of the relationships among depth, no-stop time, and surface intervals without tables.

A lot of people learned tables & didn't internalize a lasting understanding of much of that.

I learned tables in both OW & Nitrox courses. I bought a copy of, and kept, the tables for air, EAN 32 & EAN 36. I don't 'work them' for repetitive dives. I glance at them occasionally to see what dive time one could have on, say, EAN 32 at 90 feet deep (knowing a real world multi-level dive will provide more).

You raise an interesting point about how people learn with the tools available (e.g.: tables vs. computers).

Perhaps 'computers' should be taught in a way that better convey's nitrogen loading/off-loading, tissue compartments, etc..., in OW if current course work is lacking in this? I took OW in '06 before 'all computers' was an option.

Those of you who teach OW without tables, how good is the current instruction at explaining broadly about nitrogen on-gassing/off-gassing & different tissue compartments? Do you consider it comparably effective to when you taught table use?

Richard.

 

[Storker]

When I do deco diving from a boat during my winters in South Florida, before we hit the water the boat crew goes around the deck asking each team what their planned run time is.

Is this unique to deco diving in South Florida? Around here, it's SOP that the dive leader records every buddy pair's max depth and max run time before splashing. Rec and tec alike.

 

[boulderjohn]

A
Perhaps 'computers' should be taught in a way that better convey's nitrogen loading/off-loading, tissue compartments, etc..., in OW if current course work is lacking in this? I took OW in '06 before 'all computers' was an option.

Those of you who teach OW without tables, how good is the current instruction at explaining broadly about nitrogen on-gassing/off-gassing & different tissue compartments? Do you consider it comparably effective to when you taught table use?

Many people confuse learning tables with learning decompression theory. Decompression theory ("loading/off-loading, tissues compartments, etc.") is a topic in itself. Mark Powell wrote an entire book about it (Deco for Divers) without once teaching how to use tables. Many times people have taught decompression theory at the same time that tables are taught. That helps people confuse the two.

Teaching people how decompression works is different from teaching people how to plan and execute dives in order to avoid having problems with decompression. I teach students decompression theory just as I always have. They learn why their bodies absorb nitrogen when they are diving. They learn why they let it off as they ascend. They learn why they have to ascend at a certain rate (not too fast; not too slow). They learn why safety stops are beneficial. They learn that there is still nitrogen in their bodies after the dive that affects how long they have to wait until the next dive and how long they can do the next dive.

For many years, after teaching them all of that, I showed them how to plan their maximum depths using a dive table. I taught them how to plan their surface intervals using a dive table. I taught them how to plan subsequent dives using a dive table. I taught them that if they violated the no decompression limits of the table, they had to go to a pretty drastic emergency decompression plan and say out of the water for a very long time because the tables did not have the ability to deal with required decompression.

With the current course, after teaching them all of that, I show them how to plan their maximum depths using a computer. I teach them how to plan their surface intervals using a computer. I teach them how to plan subsequent dives using a computer. I teach them that if they violate the limits of the table, they have to understand the way the computer is guiding them through a safe decompression and that they may have to stay out of the water a little longer before the next dive because the computer has the ability to deal with required decompression.

Decompression theory is one thing; the way we deal with it on a dive is another.

 

[2airishuman]

For many years, after teaching them all of that, I showed them how to plan their maximum depths using a dive table. I taught them how to plan their surface intervals using a dive table. I taught them how to plan subsequent dives using a dive table. I taught them that if they violated the no decompression limits of the table, they had to go to a pretty drastic emergency decompression plan and say out of the water for a very long time because the tables did not have the ability to deal with required decompression.

They needed better tables.

https://www.divegearexpress.com/buhlmann-air-dive-table-w-optional-50-accelerated-deco

PADI's approach with the tables is to leave off the deco schedule, presumably because they believe that making such information less readily accessible will discourage people from deliberately exceeding no-stop limits.

None of the dive computers are dumbed down in this fashion. Maybe more people deliberately exceed no-stop limits as a result. ::shrug::

As an aside, I think the condensed IANTD table layout is more helpful than the PADI RDP for the sort of general planning that people conduct in the dive computer era.

With the current course, after teaching them all of that, I show them how to plan their maximum depths using a computer. I teach them how to plan their surface intervals using a computer. I teach them how to plan subsequent dives using a computer. I teach them that if they violate the limits of the table, they have to understand the way the computer is guiding them through a safe decompression and that they may have to stay out of the water a little longer before the next dive because the computer has the ability to deal with required decompression.

The interesting instructional question, to me, is: How do you teach them rules of thumb and general dive limits? Do you have them calculate the no-stop limit for a bunch of hypothetical dives?

 

[boulderjohn]

They needed better tables.

https://www.divegearexpress.com/buhlmann-air-dive-table-w-optional-50-accelerated-deco

PADI's approach with the tables is to leave off the deco schedule, presumably because they believe that making such information less readily accessible will discourage people from deliberately exceeding no-stop limits.

None of the dive computers are dumbed down in this fashion. Maybe more people deliberately exceed no-stop limits as a result. ::shrug::

As an aside, I think the condensed IANTD table layout is more helpful than the PADI RDP for the sort of general planning that people conduct in the dive computer era.



The interesting instructional question, to me, is: How do you teach them rules of thumb and general dive limits? Do you have them calculate the no-stop limit for a bunch of hypothetical dives?

I am going to try to be a bit careful in this response. The last time a brand new diver told me I was wrong about everything, I am afraid I got a bit sarcastic in that response. Your ScubaBoard profile says you are not yet certified--is it up to date? Are you certified now?

I am well aware that there are different kinds of tables, and I am well aware of their histories. I have taught that stuff for years when I teach decompression theory to divemaster candidates and technical divers. I am especially well versed on the theory behind the PADI tables. It would take me quite some time to explain it all for you, and I am not sure you would be receptive to that learning. After all, you are already lecturing on that history based on what are admittedly your presumptions, and I am not sure you would welcome information that contradicts those presumptions. That history of the PADI tables has been well documented if you would like to look it up yourself. You might find it interesting.

As for your questions about rules of thumbs and general dive limits, I have to admit I don't know what rules of thumbs and general dive limits you are talking about, so I can't respond. I imagine if I thought there was a rule of thumb that I thought would be useful, I would teach it by starting with "Here is a good rule of thumb you might find useful...."

 

[2airishuman]

I am going to try to be a bit careful in this response. The last time a brand new diver told me I was wrong about everything, I am afraid I got a bit sarcastic in that response.

I re-read my post twice and don't quite see where I said you were wrong about anything.

Your ScubaBoard profile says you are not yet certified--is it up to date? Are you certified now?

Yes. No. Let's cut to the chase and just call me a fool. It will save everyone time. I participate in the forum to try to understand things better.

I am well aware that there are different kinds of tables, and I am well aware of their histories. I have taught that stuff for years when I teach decompression theory to divemaster candidates and technical divers. I am especially well versed on the theory behind the PADI tables. It would take me quite some time to explain it all for you, and I am not sure you would be receptive to that learning.

Great, I wish you were local, I'd take a class from you. I like instructors who have a solid grasp of the subject material and are therefore able to identify and point out any misconceptions that I may have formed.

After all, you are already lecturing on that history based on what are admittedly your presumptions, and I am not sure you would welcome information that contradicts those presumptions.

Please, easy there. I'm not trying to lecture anyone. I'm just sharing my perception, which is that PADI dumbed down the tables, and that is why there was a difference in your teaching style between using the PADI tables and using a computer. Had PADI included deco information on the RDP, then the RDP would be closer in function to the computer. If that's lecturing, on my part, I'm sorry, that wasn't the intent.

We were talking about how computers affect the instructional process. You pointed out what you see as an improvement computers provide. I pointed out that a more complete table might provide the same benefit.

That history of the PADI tables has been well documented if you would like to look it up yourself. You might find it interesting.

I'll add it to my readinglist.

As for your questions about rules of thumbs and general dive limits, I have to admit I don't know what rules of thumbs and general dive limits you are talking about, so I can't respond. I imagine if I thought there was a rule of thumb that I thought would be useful, I would teach it by starting with "Here is a good rule of thumb you might find useful...."

An example might be to review the NDLs for common dive depths. I would think that many divers might want to commit such information to memory, either for ease of general planning, or to better react to unanticipated changes in a dive plan.

 

[KenGordon]

An example might be to review the NDLs for common dive depths. I would think that many divers might want to commit such information to memory, either for ease of general planning, or to better react to unanticipated changes in a dive plan.

Computers have planning modes, those will tell you the NDL at 3m intervals.

Consider a half complicated dive with trimix and two deco gasses to some depth.

Variables include:

Depth, back gas o2, back gas helium, first deco gas o2, second deco gas o2, bottom time, ascent rate, max deco ppo2 and so switch depths.

That is probably an 8 dimension table. 5 minimum. This is what computers are for. Once you have a plan from a table the adding up required to figure out the gas requirements is a bit tedious and error prone. Again computers are made for adding up.

Tables are good for ballpark planning. I want to do 30 minutes at 30m, how will that turn out? Great, but for more complicated stuff, not so helpful.

 

[boulderjohn]

We were talking about how computers affect the instructional process. You pointed out what you see as an improvement computers provide. I pointed out that a more complete table might provide the same benefit.

Actually, I pointed out how teaching decompression theory with tables is exactly the same as teaching decompression theory with a computer. I did happen to point out one superiority of the computer over one set of tables, but that was not why I was posting and I did not come close to listing the differences between diving tables and diving computers.

Please, easy there. I'm not trying to lecture anyone. I'm just sharing my perception, which is that PADI dumbed down the tables, and that is why there was a difference in your teaching style between using the PADI tables and using a computer. Had PADI included deco information on the RDP, then the RDP would be closer in function to the computer. If that's lecturing, on my part, I'm sorry, that wasn't the intent.

So, here's the scoop. PADI created its RDP using research by its Diving Science and technology branch in the 1980s, long before the modern dive computer existed. The research team included Dr. Michael Powell, who is Dr. Deco on ScubaBoard, so he can give you inside information if you ask. At that time, dives were being done using the U.S. Navy tables, which were designed years before for a very different kind of diving than was being done by recreational divers. When Dr. Workmann designed them, he added a new theoretical compartment to the long established set, the 120 minute compartment, and he used that compartment as the controlling compartment to determine surface intervals. This led to extremely long surface intervals, which did not matter much to U.S. navy divers who usually only did one dive a day. It mattered a lot to recreational divers, who were doing very different dives and then sitting on boats a very long time before being able to get back into the water for their second dives.

The DSAT team tested hundreds and hundreds of divers using Doppler bubble imaging, which had not been done by the Navy. They did the kinds of dives done by recreational divers and looked to see what profiles were safe. Yes, people got bent. They examined the results and published the data. They determined that for the kind of diving being done, the 40 minute compartment could safely guide surface intervals. They decided to play it safe, though, and they used the 60 minute compartment instead. If you compare the tables, you will see that the Navy tables wash out in 12 hours, and the PADI RDP washes out in 6 hours. That results in a significantly shorter surface interval between dives, arguably making the kinds of dive schedules used around the world today possible.

They did something else to make it a bit more conservative--they shortened the allowable first dive times. For example, if you are diving to 100 feet on the Navy tables, your first dive can be 25 minutes. For PADI, it can be 20 minutes. This further enabled them to shorten the surface intervals.

A final difference lies in the pressure groups. PADI made many more pressure groups than in the Navy table. This made it much more accurate because it cut down on the amount of rounding off that had to be done.

Yes, they did exclude the depths requiring decompression. They figured that if you are going to do decompression, you are going to need further training, and you can get into that when you get that further training.

So is that what you mean by "dumbing down"?

---------- Post added December 8th, 2015 at 04:54 PM ----------

One more thing. You referenced the IANTD tables and pointed out that they include decompression information. It might interest you to know that IANTD was formed in 1985, after the PADI RDP was published, and its name means the International Association of Nitrox and Technical Divers. That was at the time that nitrox was just being introduced, and most agencies considered it too dangerous for recreational diving. The idea of technical diving was also brand new. Since they were formed in large part to teach decompression diving, it is not surprising that their tables include decompression.

 

[The Chairman]

Ratio Deco is fantasy based at best. More divers, per capita, get bent on that, than any PDC or other table. Probably all of them combined.

My point was not that they were the best gasses for diving cause they don't really comply for any best gas process. they are the best 3 gasses for using ratio deco that are used over a great depth range, with each gas to their own depth band. As such using them makes it easy to do the ratio deco and no longer need the reliance upon computers. The dicipline in DIR is based on use of those gasses. With out that they would be hosed. I have recently seen an article using ratio deco in recreational diving based on ean32 as a standard gas.