Sonar is a technique that uses sound propagation to navigate, measure distances, communicate with or detect objects on or under the surface of the water, such as other vessels.

In short Sonar uses sound waves to 'see' in the water.

Sonar, short for Sound Navigation and Ranging, is helpful for exploring and mapping the ocean because sound waves travel farther in the water than do radar and light waves.

Active sonar transducers emit an acoustic signal or pulse of sound into the water. If an object is in the path of the sound pulse, the sound bounces off the object and returns an “echo” to the sonar transducer. If the transducer is equipped with the ability to receive signals, it measures the strength of the signal.