Sonar is an acronym that stands for Sound Navigation and Ranging. It refers to a system used by ships, submarines or aircraft to detect objects underwater using sound waves. The sonar equipment sends out pulses of sound energy and listens for the echoes produced when these sounds bounce off nearby objects such as rocks, boats or other vessels. By analyzing the time it takes for the sound wave to return and the strength of the returned signal, the system can determine the distance, location, speed and direction of the object. Sonar is commonly used in navigation, particularly by submarines that need to navigate underwater without surfacing. It also has many other applications including mapping the ocean floor, detecting oil deposits or identifying marine life.