Towed pinger locator

[2] The locator is mounted in a hydrodynamic shell, or "tow fish", connected by winch behind a surface vessel across the search area.

The locator listens for the sound emanating from the beacon or "pinger".

Once located, the beacon and its attached recorders can be retrieved by divers, submersibles or remotely operated vehicle (ROV), depending on depth.

A model currently used by the United States Navy is the TPL-25, which has a weight of 70 pounds (32 kg) and a length of 30 inches (760 mm); it is generally towed at 1–5 knots (2–9 km/h).

Since the pinger signal is relatively weak, the hydrophone must be within a nautical mile (about 6,080 feet (1,850 m)) to detect it.