[Fish]

Originally Posted by listopencil

Why is it harder to talk to someone underwater than in air? The answer is that sound couples poorly from air to water. When you talk, you do so by emitting air and then sending compression waves through this air. Your lungs provide the burst of air, and your vibrating vocal cords and mouth imprint the appropriate sound waveform on the air. In order for someone underwater to hear you, the sound waves have to go from the air in your mouth into the water surrounding you. Sound waves have a hard time going from air into water and mostly get reflected at the air-water interface instead of being transmitted into the water. If your lungs and airways were filled with water, and if your vocal cords and lungs were tuned to handle water, you would do a better job of generating sound underwater as there would no longer be an air-water interface.


http://wtamu.edu/~cbaird/sq/2013/11/...ne-underwater/