This is an excerpt from Scuba Diving 5th Edition by Dennis Graver.
Scuba divers use several hand signals that are not used for skin diving. The signals specific to scuba diving relate to air supply. Learn and use the standard hand signals shown below. Remember to display hand signals clearly and deliberately and also to acknowledge the hand signals you receive.
Scuba diving hand signals.
Learn more about Scuba Diving, Fifth Edition.