It is known that crocodilians are able to locate the source of air-borne sound. However, locating the source of water-borne sound is difficult for physical reasons. I tested the ability of American Alligators (Alligator mississippiensis) to determine the direction toward the source of underwater sound by using their tendency to be attracted to slaps on the water surface. To produce surface slapping sounds with no air-borne component, I slapped the surface of the water inside a submerged diving bell and recorded the direction of alligator movements after the sound. The results show that alligators have a directionally biased response to water-borne sounds, indicating that they are capable of locating the source of a sound signal transmitted through the water. It would be physically difficult for the animal to do so by using the differences in time of sound arrival or in amplitude between left and right sides of the animal's head, so it is likely that alligators use other methods such as a sound pressure gradient system.