Definitions for "Echo sounder"
Keywords:  sonar, depth, asdic, pulse, seafloor
An instrument that uses sound to measure the depth of the ocean.
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; sonar is an acronym for sound navigation ranging; asdic is an acronym for anti-submarine detection investigation committee
an electronic device which emits sound waves from a ships bottom to determine the depth of the water
Keywords:  shoal, sizable, pike, sure, excellent
an excellent aid because if a shoal of herring shows on it, you can be sure that there will also be sizable pike close by