noun - Combat swimmer (or combat diver, frogman, combatant diver) is a member of the military who is trained in scuba diving or swimming underwater in a tactical capacity which includes combat. They are trained and skilled in combat swimming (or combat diving for coastal or ship infiltration as part of naval special operations.
In the U.S. military, combat swimmers are trained in scuba and are deployed for tactical assault missions. This term is used to refer to the Navy SEALs, operatives of the CIA's Special Activities Division, elements of Marine Recon, Army Ranger RRD members, Army Special Forces divers, Air Force Pararescue, Air Force Combat Controllers and the Navy Explosive Ordnance Disposal (EOD) units.
In Britain, police divers have often been called "police frogmen". The first British police diver was a policeman who, needing to search underwater for evidence of a body, did not use a drag but went home and fetched his sport scuba gear.