U.S. Navy Martin P-5 Marlin seaplane patrol squadrons, destroyers, ocean minesweepers, PCFs (swift boats) and United States Coast Guard cutters (USCGC) performed the operation. Also playing a key role in the interdictions were the Navy's patrol gunboats (PGs). The PG was uniquely suited for the job because of its ability to go from standard diesel propulsion to gas turbine (turboshaft) propulsion in a matter of a few minutes. The lightweight aluminum and fiberglass ships were not only fast but highly maneuverable because of their variable-pitch propellers. Most of the ships operated in the coastal waters from the Cambodian border around the south tip of Vietnam up north to Đà Nẵng. Supply ships from the Service Force, such as oilers, would bring mail, movies, and fuel.