Air starvation is a scary situation where you feel like you cannot breathe, and is usually the result of overexertion or an air restriction in your equipment.

If you have trouble breathing, immediately stop your activity and concentrate on slowing your breathing rate. Watch your submersible pressure gauge as you breathe, and look for movement in the needle. If the needle moves as you breathe, the cylinder valve might be partially closed. Open the valve if you can reach it, or seek assistance from your buddy if you need help.

If equipment problems are not responsible for your air starvation, you've probably overexerted yourself. If this is the case, stop your activity and relax until your breathing rate slows down to a pace your regulator can handle.