Air-sea rescue (ASR or A/SR, also known as sea-air rescue), and aeronautical and maritime search and rescue (AMSAR) by the ICAO and IMO, is the coordinated search and rescue (SAR) of the survivors of emergency water landings as well as people who have survived the loss of their seagoing vessel. ASR can involve a wide variety of resources including seaplanes, helicopters, submarines, rescue boats and ships. Specialized equipment and techniques have been developed. Both military and civilian units can perform air-sea rescue. Its principles are laid out in the International Aeronautical and Maritime Search and Rescue Manual. The International Convention on Maritime Search and Rescue is the legal framework that applies to international air-sea rescue.
Air-sea rescue operations carried out during times of conflict have been credited with saving valuable trained and experienced airmen. Moreover, the knowledge that such operations are being carried out greatly enhanced the morale of the combat aircrew faced not only with the expected hostile reaction of the enemy but with the possible danger of aircraft malfunction during long overwater flights. As such, many militaries have opted to develop a capable air-sea rescue component, and ensure that such assets are available during most deployments. Early air-sea rescue operations were performed by flying boats or floatplanes, with the first dedicated unit operating such aircraft being established near the final months of World War I. While initially restricted to in-shore operations and with limited equipment, capabilities and resources would be expanded over the following decades. By the start of World War II, various nations were operating capable air-sea rescue units that operated a combination of amphibious and land-based fixed wing aircraft.
