Depth finder and Sonic depth finder

Depth finder noun - Navigational instrument used to measure the depth of a body of water (as by ultrasound or radar).

Sonic depth finder and depth finder are semantically related in sonar topic. In some cases you can use "Sonic depth finder" instead a noun phrase "Depth finder", when it comes to topics like echo sounder, sounder.

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

Depth finder and sonic depth finder are semantically related in sonar topic. You can use "Depth finder" instead a noun phrase "Sonic depth finder", if it concerns topics such as echo sounder, sounder.