Difficulty descending is the biggest reason why people overweight themselves ... and there's a cure for it regardless of what exposure equipment they're wearing.
First ... some concepts ...
- The biggest reason why people have trouble getting down is because they are unconsciously kicking while descending ... which has the effect of sending yourself up while you're trying to go down. Have him cross his feet at the ankles. This won't stop him from kicking ... because that's a brain function that needs practice to "rewire" itself ... but it will make him aware that he's doing it, so he can take the conscious effort to begin the rewiring process.
- There's a "right" way to breathe while descending ... and it all happens within the first few feet of the descent. When you're ready to go ... when you and your buddy have exchanged the "OK to descend" signals and have raised your BCD inflator hose ... take a big deep breath in and hold it. Start letting air out of your BCD, but don't start breathing out until you're at about eye level with the surface. Now exhale slowly and completely ... and when you're done exhaling, exhale some more. You'll be surprised how much air is still in there. Never forget that your lungs are a part of your buoyancy system and it's just as important to empty your lungs completely as it is your BCD. Exhaling slowly ... and taking that extra second or two to really "push" the air out at the end ... gives you time to get a few feet underwater before you have to inhale again. If you inhale too close to the surface, the buoyancy of your lungs just sends you back up ... making you think you need more weight. You want to be at least five or six feet below the surface before breathing in.
These two simple things will make him aware if he's overweighted ... because if it's as bad as you say it is, he'll sink like a rock and likely crater into the bottom because all that extra weight will make it difficult for him to arrest his descent once you're down far enough for pressure to become your friend.
Now let's address the weight check. If bottom topography allows, I prefer doing it this way ...
- Drain your tank down to the desired reserve at the end of the dive ... typically 500 psi. This is where your tank is most buoyant, and where you want it to be for a proper weight check.
- In about 8 feet of water, let all the air out of everything ... BCD, drysuit and lungs. You should have just enough buoyancy to gently lay on the bottom. Now ... remember that fin pivot they taught you in OW class? This is about the only practical use for it. While laying on the bottom, breathe in. If you are properly weighted ... in about 8 feet of water ... you should be able to fin pivot ... chest rising off the bottom as you inhale and sinking back to the bottom as you exhale. If you have to add any air at all in order to make your chest rise on the inhale, you're overweighted. If you cannot make your chest touch the bottom on a full exhale, you're underweighted. Add or remove weights as needed to achieve a good fin pivot without any air in BCD or drysuit.
It's not uncommon for divers using this method to remove a surprising amount of lead ... and discover they never needed it in the first place ...
... Bob (Grateful Diver)
