SONAR is an acronym for the term ‘sound navigation ranging’. It is a technique that involves the usage of sound propagation for navigational purposes. It can also be used for the detection of distant objects and for communication with other objects. SONAR has a wide spectrum of underwater applications, including communication between submarines and navigation of submarines. The two types of technology that fall under the name ‘SONAR’ include passive SONAR (used to listen to the sounds made by underwater objects) and active SONAR (which involves the emission of sound waves and waiting for the echo to come back). The first person to use the concept of SONAR was Leonardo da Vinci who, in the year 1490, inserted a tube into the water in order to hear the sounds made by certain vessels.