The San Diego Sheriff's Department Underwater Search and Recovery Team (USAR), formed in 1982, is the largest volunteer team of law enforcement divers in the United States. Thirty men and women serve on call 24 hours a day to investigate crime scenes, conduct evidence searches, respond to emergencies involving natural disasters and retrieve bodies of drowning or water-related accident victims. All the principles of land-based law enforcement work preserving and collecting evidence apply underwater for USAR. USAR divers' training covers 32 separate areas, including: (1) airborne deployment of divers and gear; (2) climbing and rappelling, with and without diving gear; (3) cold water and ice diving; (4) diving physics; (5) firearms training; (6) night diving; (7) recompression chamber use; (8) search management; (9) surface-supplied air and communication systems; and (10) wreck diving.