The US Navy, like the USAF, was not well equipped for combat SAR at the start of the war in Southeast Asia.  The UH-2 Seasprite was used as a plane guard aircraft for local rescue near the aircraft carriers and their escorts on which it was based and the SH-3A Sea King was used for ASW duties.  Both helicopters were used for SAR and both were modified to incorporate armour plate, door guns, extra fuel and other features essential for the role.  The UH-2 was limited in range and endurance but was fast and presented a smaller target and served well in the SAR role.  As there was little requirement for the SH-3 to perform its primary role of submarine detection in the Gulf of Tonkin many of them were stripped of ASW equipment, fitted with armour and door guns and transferred to the SAR role.  The UH-2 and the SH-3 were also based on the destroyers and other vessels that fulfilled the function of mobile SAR bases in the Gulf of Tonkin.  Two operating stations were established, the northern station and the southern station, and when air operations were mounted, helicopters were deployed to these destroyers to be prepared for a rescue attempt.  Helicopters were airborne just offshore as raids were in progress and much of the Navy’s SAR success was due to the short reaction time that this forward basing permitted.  The Navy helicopters were originally operated by detachments of existing squadrons and it was not until 1 September 1967 that a dedicated SAR squadron, HC-7, was formed to replace the UH-2 detachments.  A system known as High Drink was devised that allowed a helicopter to lower a hose to a ship that was not fitted with a flight deck so the helicopter could take on fuel while in the hover.  The helicopters came to be known by their radio call signs, Clementine for the UH-2s and Big Mother for the SH-3s.  The Navy SAR effort was rather piecemeal and low-key compared to that of the Air Force.  This is reflected in the survival rate of airmen shot down over North Vietnam.  Thirty-one percent of USAF airmen were rescued by SAR forces during the war compared to just 16 per cent of US Navy airmen although these figures probably do not give a true picture as Navy helicopters sometimes rescued USAF airmen and vice versa.