Another addition:
Many divers dump as much gas as they can. The makes them really negative from the get-go, and uber-negative as they reach depth. A [-]better[/-] different idea is to dump just as much as you need to in order to break the surface, and to then continuously add gas to your BC throughout the descent to maintain as close to neutral buoyancy as possible. Descending at a constant rate makes the whole thing much easier to control, and you can stop on a dime if you need to. On the other hand, if you are negative throughout the descent, you will be accelerating downwards (at least until you hit terminal velocity), and you'll have to add a ton of gas to stop.
