A sonar pulse sent from a ship hits a submarine and returns after 0.90 s. Speed of sound in seawater is 1530 m/s. The distance to the submarine is:

The pulse goes to the submarine and back in 0.90 s — so one-way time is 0.45 s. Distance = speed × time = 1530 m/s × 0.45 s = 688.5 m. SONAR (Sound Navigation and Ranging) uses this principle to locate underwater objects, exactly as bats do above water.