An acoustic signal or sound pulse is sent into the water by active sonar transducers. The sound pulse will bounce off an item if one is in the way of the sound pulse, sending a "echo" back to the sonar transducer.
SONAR is most useful underwater, although it also functions in the open air. The reason for this is that sound travels farther in water.
Sonar devices use sound waves to penetrate the ocean and record the sound waves that are reflected back to display items below the surface. This is known as active sonar, which is a type of echolocation similar to that employed by bats. Similar technology exists in radar, but radio waves are used in it.
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