Patrol Craft Fast (PCF), also known as Swift Boats, were all-aluminum, 50-foot (15 m) long, shallow-draft vessels operated by the United States Navy, initially to patrol the coastal areas and later for work in the interior waterways as part of the brown-water navy to interdict Vietcong movement of arms and munitions, transport South Vietnamese forces and insert SEAL teams for counterinsurgency (COIN) operations during the Vietnam War.