Fathometer and Sonar

Fathometer noun - Depth finder for determining depth of water or a submerged object by means of ultrasound waves.

Sonar and fathometer are semantically related. In some cases you can use "Sonar" instead a noun "Fathometer".

Sonar noun - A measuring instrument that sends out an acoustic pulse in water and measures distances in terms of the time for the echo of the pulse to return.

Fathometer and sonar are semantically related. You can use "Fathometer" instead a noun "Sonar".