An unmanned lifeboat (1) has a hull (2) with a transom opening (3), a fo'c'sle (4) closed by a rounded top deck (5), providing accommodation (6) for survivors. The aft deck as such is generally U-shaped with a cut-out (16) open at the transom (17), which is vestigial with two small port and starboard parts. Within the cut-out is a boarding assistance ramp (18). This is level with the aft deck at its forward end and slopes down to the transom. It extends aft of this by a few of feet - say about 1m - to enable survivors to swim and crawl onto it. For guidance to reach the vicinity of the survivors, the lifeboat is equipped with a communication apparatus including a receiver (32) for receiving survivor location data. In addition, the navigation apparatus with which the lifeboat is equipped includes a GPS system (33) of its own, a compass (34). The lifeboat is also equipped with a control system (35). The latter computes a course to the survivors by comparing its and survivor positions. The control unit has an output module (36) for controlling the propulsion units to drive the lifeboat to the survivor position, making a final approach at slow speed. The control system is also programmed to perform a search around a last known survivor position in case they cannot be otherwise located, taking account of dead reckoning due to wind and tide.