from the crackling of snapping shrimp, to the whistles of dolphins; from the crash of a wave on a rocky coast to underwater earthquakes, the sea is far from silent. Humans contribute to the soundscape as well, in minor and major ways – for instance, recently there has been significant exposure to the harmful effects of SONAR on whales.
Sound in the sea is especially interesting for the very fact that it is under water, and so has different properties. In particular, water is denser than air, so the sound pressure waves travel faster. This is part of why when we are underwater it is difficult to localize where a sound is coming from.