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Amen to this thread! While doing my certification course, I kept on at my instructor about knowing how long I will be able to stay under water with different tanks and how I could "plan my dive, and dive my plan" if I couldn't make a plan because I didn't know how long a tank would last me...frustrated me when all I could get for the most part was that you should be done your dive with 500psi..well..dammit..that doesn't help me plan my dive. At that point I didn't really understand that we weren't touching anything but "recreational" diving, and understand now why they don't teach it...but sure wish they would.
My dear dive buddy, with whom I just took and passed GUE's Cave 1, has a SAC rate of about .75. He's one of the most beautiful divers I know, quiet and steady in the water, very relaxed, beautiful technique. He's just 6 feet tall and made of muscle, and he uses gas. It's just how it is, and it's fine. I'd much rather he breathe as much as he needs to, even if it limits our dive, than have him play with techniques to reduce gas consumption that result in CO2 retention.
I don't think all dives to 100 feet need to be done as staged decompression dives. I'd better not think that, because I dive to 100 feet fairly often, and I don't do staged decompression, or at least not the kind most people think about when they say that. But I do think that the combination of increasing gas reserves and short "no deco" times below that add up to less and less useful time there. If your dive is a multi-level dive, where you descent to 130 to look at an anthia and then spend the whole rest of the dive working your way up the wall, that may be manageable within reasonable reserves and still give you enough fun to make it worth while. But square profile dives to depths below 100 feet, even on Nitrox, begin to get pretty short.
When I dive to 100 feet, I do it in doubles and on 32%. When I dive below that, I do it in doubles and on 25/25.
My dear dive buddy, with whom I just took and passed GUE's Cave 1, has a SAC rate of about .75. He's one of the most beautiful divers I know, quiet and steady in the water, very relaxed, beautiful technique. He's just 6 feet tall and made of muscle, and he uses gas. It's just how it is, and it's fine. I'd much rather he breathe as much as he needs to, even if it limits our dive, than have him play with techniques to reduce gas consumption that result in CO2 retention.
Divers need to understand that, I use single big tanks and almost never try to reduce respiration to save air.
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SCUBA Diving: The only sport where grown men will brag about how low their sac is.
Consider including a deep stop in your rock bottom.
Can you help me out with some guidelines on this. How deep? How Long?
Deep stops are getting more popular to help keep down bubble size growth. From what I've heard, some recreational agencies have/are looking at incorporating it into their recommendations.
There seem to be several forms, all fairly similar, which I interpret as meaning that the details don't have to be terribly precise to get most of the benefit.
They general run something like: Take your max depth. Your first deep stop is at half that depth. Take that depth and divide by two again. Do another deep stop if the resulting number is deeper than 30'. Repeat until you come up with a number shallower than 30'.
Each deep stop is one minute. You don't want much longer at depth, to avoid on-gassing too much additional nitrogen.
Some divers, often those with technical/deco training, prefer to do a one minute stop every ten feet, starting at the first deep stop.
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