The full form of SONAR is Sound Navigation and Ranging. It is a sound technology that uses the propagation of water for the purpose of navigation underwater. It is also used to communicate, or detect objects under the surface of the water. The concept was first developed by Leonardo Da Vinci, who had given the structural aspect in the year 11490, and also first practically tested the concept by using a tube inserted into the water to detect the vessels by the ear. The concept was first given the proper formation and was practically used during World War I, to account the increasing Submarine Warfare.

There are essentially two types of SONAR, Active Sonar, which is comprised of transmitter and receiver. The transmitter transmits high frequency towards the targeted objects and the receiver receives the vibration of the moving objects under water that is reflected back from the object due to the high frequency.

Passive sonar, is comprised of a receiver which received the waves of the river or the water, and detects the underwater movement. It only detects the noises made by the underwater objects. The prime point of the passive sonar is that it does not have any sound of its own.

The SONAR technology has benefitted the countries in many ways. Not only it has a significance in case of military warfare, but it also helps the fishermen to find out the school of fish. It also helps in underwater navigation, velocity management, wave measurement and biomass estimation.