A sonobuoy is a small, expendable sonar system used primarily by naval forces to detect underwater objects such as submarines. Deployed from aircraft or ships, it floats on the ocean surface while its sensors descend underwater to transmit acoustic data back to operators via radio signals. Sonobuoys are essential tools in anti-submarine warfare (ASW), enabling real-time tracking and surveillance of underwater threats. They come in various types, including passive (listening only) and active (sending and receiving sound pulses), and are designed for short-term use in tactical operations.