It's not my intention to hijack this thread, but I have a practical question about checking weights in a new dive location. In August, me and my son will be diving in Cozumel for the first time. This will also be out first salt water dive. Assuming we don't get wet until we are above the reef, ready to dive, how do we properly determine the amount of weight needed for each of us?
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n733lk: For determining weighting needs on a Cozumel trip, the best approach is to conduct a proper weight check on a shore dive prior to doing any boat dives.
If this cannot be done, then I would recommend asking the boat op
and DM if it would be possible to do a weight check while hanging off of the back of the boat prior to doing Dive #1. You need to ask about this ahead of time because your weight check will impact the plans of the DM-led group. On account of this situation, there will be a certain amount of time pressure placed on you and your son. Expect it and deal with it.
There is another option that could work if you know what kind of tanks you'll be using in Cozumel. FYI, most dive ops use AL80 tanks. Simply conduct a weight check in a local pool (fresh water) in
all of the gear that you'll be using in Cozumel, including an AL80 tank. Then add enough weight to compensate for the greater density of salt water vs. fresh water. This is approx. 2.5% of your total weight (diver + diver's gear). For most people, this is works out to an additional 6-7 lbs.
If you can't do a weight check on-site in Cozumel prior to doing a boat dive, then it might be a good idea to take a couple extra lbs. as insurance against being too light at the end of the dive.
Please don't be
that guy on the boat who gives a blank stare back to the DM when he asks: "How much weight do you need?" I've witnessed it several times on a Cozumel dive boat.
OK Windapp, Here is what I have done in a particular run away descent & ascent.
Descent-
I was a Dive Master for an instructor who had a student who overweighted himself to make descending easier. The plan was to drop to 20 ft over a depth of about 90 ft & then swim along a wall to the shallow area of the quarry & then to a training platform. The instructor was at the head of the group & I was bringing up the rear. Once the student got to depth, his suit compressed & the weightbelt slipped off his hip & below his butt. AT that point he went into a passive panic & quit kicking, then started sinking. Seeing his distress I swam over quickly, but by the time I got to where he was, he was sinking very quickly. I went head first after him (my ears equalize very easily) & caught him by his cylinder valve at 70 ft. I was wearing a BC with a large lift capacity & just used my BC to start us to the surface, along with swimming both of us out. It was not a run away ascent, but we probably came up a little faster than we should have. I got the student situated & got him to the platform where the rest of the class was. I later informed the instructor what had transpired.
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windapp: The rescue maneuver that
tstormdiver describes above is something that might be appropriate for a DM to do. If you are a novice and have not received rescue training, you really have no business even attempting what she did. If you do what she did (use your own BCD's lift to slow down your buddy's descent) and accidentally let go of your buddy, both of you could be in a great deal of danger. The extra air inside your BCD is sure to lead to an uncontrolled ascent for you. Once you separate from your buddy, he'll be very negatively buoyant and he'll plummet downward. Hopefully, the descent was undertaken over a hard bottom.
