Submarines Navigate Using "Echolocation"

The best known application of echolocation in humans is in the field of submarine navigation. Since the 1940's, submarines have used the echo of strong pulses of sound to determine where the ocean floor is and identify other obstacles like reefs, islands, continental formations or whales. The returning sounds are relayed via headphones to a specially trained technician who's job it is to interpret these sounds, and to guide the submarine and its crew safely through complete darkness.

Submarine sonar technicians are basically blind.  The water pressure at these depths  make it impossible to put windows to the outside of the submarine leaving them with only their sense of sound to detect objects. It is a bit different than echolocation in air because sound travels differently in water than in air. (more about that in another post)  Basically, it is subject to differences in water pressure as you will see in this video, but it also has it's own pressure propagation characteristics that are intriguing. (See Wikipedia article on Speed of Sound.)