While they do not have external ears, fish are able to perceive underwater sounds through their internal ears. Fish pick up sounds through both their internal ears and lateral lines down their bodies.
According to Ocean Conservation Research, fish rely on a range of acoustical adaptations to perceive sound, including the ability to sense movement in the water. Fish rely on their internal ears for balance in much the same way human beings rely on their inner ears to maintain equilibrium. LiveScience points out that human ears evolved from fish gills, while certain fish characteristics are the results of genes shared by human beings.