SONAR (an acronym for SOund Navigation And Ranging) was a technique that used sound waves to navigate, communicate, or detect other objects under water.
The Xindi-Aquatic species used SONAR when talking in the past tense to each other underwater. (ENT: "The Council")
- RADAR, a similar technique that utilized radio waves projected through the air.
- LIDAR, a similar technique that utilized light waves projected through space.