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I had casually suggested to Lynne, my wife, that she learn how to dive so that we could dive here in Puget Sound and also in the tropics. While she was somewhat open to the idea of diving in the tropics, there was no way she would ever get into the cold, dark waters of Puget Sound. This was something that was not pursued so the topic always dropped -- until one fateful eve she bid, and bought, a trip to Australia at a school auction. Since we already were planning on a sailing vacation to the British Virgin Islands, I demanded (perhaps the only time in our marriage) she learn to dive -- she acquiesced.
Let's just say she was not a "natural diver" and she had just about every issue a new diver can have. IF you are at all interested in learning to dive but think "It is not for me" please read her journal.
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When you first learn to dive in the Open Water Class, every student is told to "Plan your dive and Dive your plan." While time is spent making sure that every diver understands the concept of "No Decompression Limits" and how "NDLs" limit the amount of time you can safely spend underwater, often little is taught about planning for how much air you actually need for the dive. This is the topic of Air Supply Management which is often referred to as Gas Management.
In the spring of 2009, I was asked to present a lecture on this topic and you can find the PowerPoint Presentation here (in PDF format).
I have also created an "Air Supply Cheat Sheet" which, in one page, summarizes the topic:
I will teach you about Air Supply Management in his Nitrox and Deep Diver Specialty Classes -- and will touch on the subject at every other appropriate teaching opportunity!
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"Technical Diving" is often defined as Advanced Recreational Diving and the biggest difference between "Recreational Diving" and "Technical Diving" is that in Recreational Diving, if you have a problem under water, you can, and should, go to the surface to fix it. However, in Technical Diving, going to the surface is NOT an option when the diver is confronted with a problem. The diver may be deep inside a Cave (even not very deep, 400 feet for example, is too far to swim on a single breath), inside of a wreck or have a mandatory decompression obligation (the so-called "virtual" ceiling). Technical divers learn techniques to minimize the dangers they face and maximize their ability to solve problems underwater.
In the summer of 2007, Dive Training magazine published an article describing what the Recreational Diver could learn from the Technical Diver. I thought it was an interesting article -- here it is.
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A friend of mine, Lamont Granquist, has written a very good explanation of the concept of minimum gas reserves -- aka Rock Bottom, aka, how much gas do I need to be safe on my dive? I have used a lot of his information when I wrote the Air Supply Management paper, above, and the "cheat sheet" which is also above.
For people who really want to be able to "plan their dive" so that they can safely dive their plan, this is a concept to be followed.
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There are times when you just don't have two hands to flash numbers to your buddy, it's dark and one hand has a light, one hand is carrying a camera, etc. But you still need to let your buddy know your PSI or that you want to go up to 65 feet, or whatever. That is when you need to be able to calmy, and clearly, use the One Hand Numbering System. The two keys to the system are:
a. The orientation of the hand gives the numeral -- fingers point up and palm facing buddy are 1 - 5; fingers point horizontal and palm facing you for numerals 6 - 9; and
b. The use of the Zero is optional because the numbers are used in context -- Two, Five when referring to tank pressure had better be 2500 and NOT 25 psi!
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The following was written for the PADI Undersea Journal and was published in an edited form, 4th Q, 2012.
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