Patrol Boat, Riverine, or PBR, is the United States Navy designation for a small rigid-hulled patrol boat used in the Vietnam War from March 1966 until the end of 1971. They were deployed in a force that grew to 250 boats, the most common craft in the River Patrol Force, Task Force 116, and were used to stop and search river traffic in areas such as the Mekong Delta, the Rung Sat Special Zone, the Saigon River and in I Corps, in the area assigned to Task Force Clearwater, in an attempt to disrupt weapons shipments. In this role they frequently became involved in firefights with enemy soldiers on boats and on the shore, were used to insert and extract Navy SEAL teams, and were employed by the United States Army's 458th Transportation Company, known as the 458th Sea Tigers. The PBR was replaced by the Special Operations Craft – Riverine (SOC-R)
Typical armament configuration included twin M2HB .50 caliber (12.7 mm) machine guns forward in a rotating shielded tub, a single rear M2HB, one or two M60 7.62 mm light machine guns mounted on the port and starboard sides and a Mk 19 grenade launcher. There was also a full complement of M16 Rifles, shotguns, .45 ACP handguns and hand grenades. Some had a "piggyback" arrangement, a .50 cal machine gun on top of an 81mm mortar; others had a bow-mounted Mk16 Mod 4 Colt 20 mm automatic cannon, derived from the AN/M3 version of the Hispano-Suiza HS.404 and also found on the LCMs and PBRs.
What the boats possessed in heavy firepower they lacked in armor or shielding. Although the .50 cal machine guns had some ceramic armor shielding and the Coxswain's flat had some quarter-inch thick steel armor plate, the boats were designed to rely on rapid acceleration, maneuverability, and speed to get out of tight situations.