An instrument for measuring the depth of a body of water: In her oceanography class at college, Susan learned that a bathometer was used to ascertain the depth of the sea, but it is rarely used in the present time.

A sounding line was used previously with a bathymeter, but it proved to be quite difficult and a time-consuming procedure.

The bathometer does not require a line to extend to the bottom because it measures the difference in the gravitational effect of the water surface and of solid ground.