Hello friend @afterglow.
Acoustics is a wonderful branch of physical science which is responsible for the study or analysis of the phenomenon of sound, infrasound and ultrasound, and among the sub-branches of acoustic science is the sub-aquatic acoustics and this branch is dedicated to the study of sound waves (sound) in the water and the same implemented for the detection of any object within a given volume of water, technique used both in ships as in our figure 6, as in the impressive machines which we call submarines.
Thanks for your important contribution, many successes. Best regards.