Rhine River Patrol (US Navy) (Source: Donald Birkes, CORRPAT, Schierstein) For patrol work on the Rhine River the Navy used boats designated PR (Patrol River), that had a speed of 25 knots (29 mph). The boats were built in German shipyards to American specifications. This craft (PR33) is in the process of going through sea trials in the North Sea prior to being delivered to the US Navy in Germany. Notice the craft has no guns mounted and is flying the West German flag.