Before you enter the water, review your ABCs.
A – Make sure your Air is on by inhaling from your primary second stage while looking at your pressure gauge. If the needle drops significantly when you inhale, it indicates that the valve is either closed or only partially opened.
B – Next, make sure your BCD is inflated enough to support you at the surface. Use your auto-inflator button to be sure it works.
C – Check that your Computer is turned on and has not retreated into a surface mode or a sleep mode.
D – Put on the rest of your Dive gear, such as your mask, fins, and gloves. When you and your buddy have exchanged the OK signal and the dive master has cleared you.
E – Enter the water.