Here are 20 common scuba diving hand signals. This guide is not intended as a comprehensive dictionary to all scuba diving hand signals, but simply an overview of some of the most commonly used underwater hand signs. You will notice that I have purposefully omitted hand signals to communicate tank pressure. I have omitted these signals because divers use such a variety of signals to communicate tank pressure that to state a "standard" signal would be more confusing than helpful. Be sure to review how you will communicate tank pressure with you dive buddies before your dives.