The transmitter produces and transmits ultrasonic waves. These waves travel through water and after striking the object on the sea bed, get reflected back and are sensed by the detector. The detector converts the ultrasonic waves into electrical signals which are appropriately interpreted. The distance of the object that reflected the sound wave can be calculated by knowing the speed of sound in water and the time interval between the transmission and reception of the ultrasound.

Let, depth of the sea = d

Speed of sound in sea water = v

Time taken for transmission and reception of signal = t

∴ Time taken to travel a distance d = \(\frac{t}{2}\)

∴ Depth of the sea, d = \(\frac{t}{2}\times v\)

(∴ distance = speed x time)