If you're correctly weighted, you should be neutrally buoyant—able to make a safety stop at 15 feet with 500 psi and no air in your BC.

How to Get Neutral

The ability to achieve neutral buoyancy is one of diving's most important skills. A neutral, relaxed diver is more efficient and uses less air than a diver who constantly struggles against positive or negative buoyancy. Perfect neutral buoyancy is difficult to maintain, especially when diving with a wetsuit, because minor depth changes alter both the suit's and the BC's compression. To stay as neutral as possible:

• Stay aware. Take notice of your surroundings, particularly your depth and body position.
• Keep it close. Your BC's inflate/deflate valve should be positioned where you can easily find and use it without looking. If you are ever unsure of what button you're pushing, hold it in your field of view when using it.
• Think small. Use your inflate/deflate valve judiciously, making small adjustments and giving them time to take effect.
• Fine-tune it. Adjust your buoyancy with lung volume. Simply changing the size of a breath can alter buoyancy by two to four pounds.
• Keep your head up. In most open-water situations, try to swim with your head slightly up and your feet slightly down; both you and your equipment work better in this position. You may need to swim head-down, feet-up in some environments where your fins could cause damage or stir up the bottom.