Free SSI Science of Diving Specialty

[Steve_C]

Along the way I read "The Encyclopedia of Recreational Diving", by PADI and "The Certified Diver's Handbook" by Coleman. Would there be a benefit to taking this SSI online course?

I really liked Coleman for diver starting out.

 

[Angelo Farina]

Of course not. The point is that the model is statistically "safe enough", and safer than existing alternatives. Other than not diving.

The model proved to be safe enough when used in "normal" diving profiles. No one can vouch on the safety of these models when applied to completely crazy diving profiles. So I evaluate positively a course which warns the diver do not thrust too much the computer when the diving profile is highly anomalous.
In such cases, I always taught my student to be overly conservative: consider the immersion as square, taking into account maximum depth and total diving time until the depth of 9m. At this point ignore the computer and make all the deco stops mandated by the US Navy tables.
Any other choice is not safe enough for me, if the diving profile was a sawtooth (or jo-jo) profile.

 

[saxman242]

Along the way I read "The Encyclopedia of Recreational Diving", by PADI

If you read this in detail, you'll probably find this course to only be a higher level review.

 

[dmaziuk]

The model proved to be safe enough when used in "normal" diving profiles. No one can vouch on the safety of these models when applied to completely crazy diving profiles. So I evaluate positively a course which warns the diver do not thrust too much the computer when the diving profile is highly anomalous.

1. There's been data collected from e.g. cave dives where "abnormal" profiles are the norm. That's part of the reason reverse profiles are no longer considered "bad".

2. And? What do you tell them for non-warm-blue-water-square-profile dives: lose the computer and break out the divining rod?

 

[Angelo Farina]

1. There's been data collected from e.g. cave dives where "abnormal" profiles are the norm. That's part of the reason reverse profiles are no longer considered "bad".

2. And? What do you tell them for non-warm-blue-water-square-profile dives: lose the computer and break out the divining rod?

The computer makes a quite good job dealing with variable depth profiles: this is their job, and they do it well.
A reverse profile is quite a normal one, you reach slowly the maximum depth, and then you hit NDL and it is time to go up. I am sure that all modern computers are perfectly safe in these conditions.
What I was referring to is a SEVERELY crazy profile. Like doing 10 times in a row the exercise with the BCD of a maximum speed ascent, stop at 3m, and down again to 15m. It was a mandatory exercise in the eighties, then luckily it was removed as it was truly dangerous.
When you have 10 students to be examinated, and you follow each of them during those ascents and then you go down for the next student, and you make it 10 times... then I cannot thrust the computer anymore, because I am sure that the designers did not test its behaviour in such a crazy profile.

 

[tursiops]

I am sure that the designers did not test its behaviour in such a crazy profile.

Nor were the tables tested for this. But you use them anyway.

 

[Angelo Farina]

Nor were the tables tested for this. But you use them anyway.

Because the table's "square" profile is in any case "including" any zig-zag profile inscribed in the "square". In no way a "zig zag" profile can give you more Nitrogen in your body than the square profile.
Instead the computer will attempt to evaluate the REAL amount of Nitrogen in each tissue, giving you an estimate which is always smaller than the one considered by the table. The problem is that such an estimate can be wrong when the diving profile is extremely crazy, hence you cannot thrust it anymore. And in lack of a better estimate, the only safe way is to rely on the good, old tables. You will end up making surely more deco than required, but you will not get bent.

 

[tursiops]

Because the table's "square" profile is in any case "including" any zig-zag profile inscribed in the "square". In no way a "zig zag" profile can give you more Nitrogen in your body than the square profile.
Instead the computer will attempt to evaluate the REAL amount of Nitrogen in each tissue, giving you an estimate which is always smaller than the one considered by the table. The problem is that such an estimate can be wrong when the diving profile is extremely crazy, hence you cannot thrust it anymore. And in lack of a better estimate, the only safe way is to rely on the good, old tables. You will end up making surely more deco than required, but you will not get bent.

It is not just about N2 uptake/offgas. It is also about ascent rates....at least the computer tries to monitor this and take it into account, the tables do not. And your zig-zag profile has a lot of ignored ascent rates if you are on tables.

 

[dmaziuk]

Because the table's "square" profile is in any case "including" any zig-zag profile inscribed in the "square". In no way a "zig zag" profile can give you more Nitrogen in your body than the square profile.

Sorry, no: this is only true because you never reach the max depth that you planned for. You never absorbed your planned amount of nitrogen and that's why it's "safe". If you follow this ad absurdum, you'll arrive at a very safe dive plan for a "craziest" profile with bottom time of 0 minutes.

You can emulate this with a computer by turning its safety factor to 11. Dive a GF 1/1 and you'll be just fine. (In principle: not that a real life computer would let you go quite that far.)

 

[loosenit2]

I just finished the SSI Science of Diving course. First of all I want to thank @Sloeber for kindly making the offer. It was an interesting course. All my certs have been through PADI so I used this as a way to evaluate the SSI online training delivery program and SSI course materials. (I've been doing the same with the RAID materials). My thoughts on the delivery method and course materials below:

Delivery. The online delivery method is very intuitive and easy to navigate and use. You have to create an account in My SSI and then the dive center signs you up for the course. You launch it and move through the course taking quizzes and then the final exam.

Course Contents. Overall the course was updated and well put together. I think that the science of diving fits into the SSI program as a required academic portion prior to DM training, and that shows. The class is divided into 5 sections: The Physics of Diving, The Physiology of Diving, Decompression Theory, The Components of the Total Diving System and Accessory Equipment, The Aquatic Environment. All in all it took me about 5 hours to work though taking notes as I went and another 30 minutes for the final exam. (I might have gone quicker than others as I recently finished Deco for Divers and have been working on RAID tech diving material so not much was new)

The Physics of diving was the most comprehensive and also the most disappointing. It covered measurements, gas laws and presented a good number of formulas for calculations. It was very well written and very thorough, in fact much better written then the RAID materials. It was disappointing because while it presented gas laws and formulas it offered very little in terms of practical exercises to drive home the math. The section included a portion of Air usage and supply but only covered SAC and not RMV and did not present info on calculating cylinder volume, although there were questions on that in the exam.

The Physiology of Diving was very in depth and interesting.

Decompression Theory was extremely thin. Basically went over a few basic concepts and then transitioned to a review of dive computers, multi-level diving, and no-fly times. This section was definitely written for a purely recreational diver, not as foundation for any technical diving or truly understanding decompression theory.

The Aquatic Environment and Equipment review were basically a review of Open Water 101 and Rescue/First Aid classes.

Would be very interesting to hear other perspectives on this course, where it fits into the overall SSI program and DM training.