Scuba divers have a hard time determining the direction of sound underwater because sound travels five times faster in water than it does in air. On land, we have a split second to detemine the direction of a sound, but underwater, sound travels faster than we can determine where the sound is coming from.
INDEX FINGER AND THUMB TOUCHING TO FORM A CIRCLE This means okay and is used as a question and an answer. PALM FLAT FACING DOWN, THEN TILTING IT SIDE TO SIDE There's something wrong. Always point where after this hand signal so that people will know what's wrong. 'THUMBS UP' GESTURE Ascend. 'THUMBS DOWN' GESTURE Descend. PALM FLAT FACING DOWNWARDS, THEN MOVING IT FROM LEFT TO RIGHT A COUPLE OF TIMES Level off or stay at this depth. This is good for your safety stops. FIST WIT