Seals: the abbreviation of land, sea and air in English, and the full name is the amphibious force of the US Navy. Its core penetration reconnaissance group 1962 is established on the basis of underwater blasting group, which mainly carries out reconnaissance of the enemy and sneak attack. He participated in various battles in Cuba, Vietnam, Grenada, Panama and the Gulf. The force consists of three naval special warfare groups (one of which is the development group), and 1 special warfare groups are deployed on the east and west coasts; The two special warfare groups have special warfare forces, three sea, land and air infiltration reconnaissance groups, one sea, land and air transport group and three or four special warfare landing forces respectively. In addition, as a reserve force, the US Navy also has six special operations group units, three special operations force units, six sea, land and air infiltration reconnaissance units and two sea, land and air transport units. The tasks of SEALs include reconnaissance, defense cooperation, unconventional warfare, direct action and counter-terrorism. When performing direct attack missions, SEALs usually use the form of a two-person combat team. The team consists of a sniper and an observer, equipped with a 0.5-inch large-caliber sniper rifle.