Sound is louder in water than in air. Sound travels as waves that bounce off objects. Sound waves travel five times faster in water than in air, and they travel farther.
The world's oceans are noisy places. According to the Student Society for Science, though the underwater world may sound relatively quiet to human ears, the noise level has been rising by 3 decibels every decade since the 1960s. Humans cannot hear many of the frequencies found in the oceans. The sounds they can't hear are heard and used by ocean-dwelling animals. Additional noise produced by ships' engines create havoc for animals that use sound for communication and navigation.