Altitude/DPV/Equipment

[pauldw]

I'm revisiting the idea of taking some specialty classes. Are these three classes worth the money, or are they just follow your computer/mind your buoyancy/here's some gear in the shop you could buy?

 

[_Ralph]

A real DPV class is worth it (ie GUE DPV1)

I can’t comment on others courses aside from I’ve seen divers with no concept of how far they can go on their scooter, and what to do when things go wrong....

Coming from a diver who dives at altitude and services my own gear while having fun with DPV’s


_R

 

[rsingler]

Of the three, I'd say that Altitude was worth the effort, especially for the theory. Yeah, just follow your computer, but altitude diving, especially at Lake Tahoe (6000'), is rather unforgiving of mistakes.

Equipment is a waste of time. If you think it's going to teach you how to understand regulator service, if not be certified in it, it's not.

DPV might be cool. But I don't scooter, so I don't know if what you learn keeps you safer. I'll leave that one for other folks to judge. Ah! @_Ralph has me covered.

 

[rongoodman]

Where are you located? A cavern class, GUE Fundies, or something similar would probably be more useful in terms of actually developing your diving skills.

 

[Jack Hammer]

A proper scooter class from someone who understands technical diving is quite worthwhile and useful for recreational diving. OTOH, if it's something like a distinctive specialty or most the AOW courses I've seen taught by basic recreational instructors then odds are it's not as worthwhile. YMMV

 

[boulderjohn]

As someone who has taken a serious interest in altitude diving in recent years and has written articles on it, I have mixed feelings about taking an altitude course. Here are the reasons:

1. In the present PADI version of the course, much of the time is spent explaining how to make adjustments when using tables. If you don't use tables, that time is pretty much wasted. (I don't know about the courses for other agencies.)
2. While a course will teach you the primary reason to be concerned, IMO it does not go into enough detail on that subject or on some other subjects (like differences in buoyancy control). If you have an instructor who knows all of this well, you'll be fine, but after more than a decade of discussions about this, I know a lot of instructors don't understand the "why" of those topics well enough to expand on them.
3. The need to be concerned about altitude varies with the specifics of the dive, and your need for the course depends upon what you plan to do. The higher the elevation, the deeper the dive, and the longer the dive time, the more you need to be concerned. If you are at (say) 3,000 feet doing a relatively benign recreational dive with a computer that automatically adjusts for altitude, you really don't have to give it a second thought. If you are doing a technical dive at (say) 6,000 feet, you need to know what you are doing. If you are diving above 10,000 feet, the US Navy manual says don't do it without special permission, and it says it in bright red, bold type. If you are planning a technical dive above 10,000 feet, better consult with a true high altitude decompression specialist (NASA has them) before you dive.
4. The course does not include some topics, like adjustments to MODs for nitrox. If you go to your average instructor and ask how to adjust MODs for altitude, my wild guess is that many (and perhaps most) instructors will have never given it a thought, will apply what they believe to be a logical process to arrive at an answer, and tell you something completely wrong. When I did my first high altitude nitrox dive (I was not an instructor), our group was led by an instructor who had us adjust for altitude. I didn't question it then, but I now know he was dead wrong. (Because I do mostly technical diving at altitude, I created MOD tables for that altitude, and those are the ones we follow. The difference is significant.)

 

[pauldw]

If you are diving above 10,000 feet, the US Navy manual says don't do it without special permission, and it says it in bright red, bold type.

Well, that's the problem. I mainly want to get some more information before doing a single dive, which will take me from my home at 4,500' up a trail to about 10,400', for a short dive into a very small lake that probably isn't more than 10-15' or so deep, in order to increase my safety a bit. I doubt it'll do much in that regard, but hopefully there'll be some theory that'll be of general use.

 

[boulderjohn]

Well, that's the problem. I mainly want to get some more information before doing a single dive, which will take me from my home at 4,500' up a trail to about 10,400', for a short dive into a very small lake that probably isn't more than 10-15' or so deep, in order to increase my safety a bit. I doubt it'll do much in that regard, but hopefully there'll be some theory that'll be of general use.

I have dived at that altitude. At 10-15 feet you won't have too much problem during the dive. The main problem will be acclimatization. That is the real reason for the US Navy warning, and contrary to what you might expect, it will continue to affect you even when you are breathing compressed air on the dive, but at your planned depth it should not matter all that much. Give a lot of time for your body to adjust to the altitude before the dive--getting into your gear and getting into the water may be the hardest part.

 

[J-Vo]

I have dived at that altitude. At 10-15 feet you won't have too much problem during the dive. The main problem will be acclimatization. That is the real reason for the US Navy warning, and contrary to what you might expect, it will continue to affect you even when you are breathing compressed air on the dive, but at your planned depth it should not matter all that much. Give a lot of time for your body to adjust to the altitude before the dive--getting into your gear and getting into the water may be the hardest part.

I'll add, having a PDC that continually calculates your tissue loading 24/7/365 like a Shearwater will add to the safety as they will know you just came up from lower altitude and take this into account for you dive. My understanding is that most recreational PDCs just measure the surface pressure when you turn them on and only calculate tissue load in the water so they would miss the loading from traveling to altitude.

 

[boulderjohn]

One more note on very shallow diving at10.500 feet....

Don't be surprised if you find buoyancy control more difficult than usual. (The reason for this is not covered in the altitude specialty class.)

Spoiler

If you have 2 liters of air in your BCD at 17 feet FFW at sea level and go to the surface, it will expand to 3 liters. If you do the same thing at 10,500 feet, it will expand to 3.54 liters. The same will be true of all other gas bubbles, as in a drysuit or wetsuit. Thus, minor changes in depth will have a greater than normal effect on buoyancy.