It's amazing to think that sailboats were used to patrol off U.S. coasts in the early days of World War II. A documentary about this ad hoc force, informally called the "Hooligan navy," is available for streaming at the National Sailing Center & Hall of Fame's online Film Library.
"The Hooligan Navy" tells a little-known story about the Corsair Fleet, a band of young yachtsmen and fishermen who were recruited into service – their vessels "armed" – so they could patrol the coastline of America's Eastern seaboard and, if necessary, engage Nazi U-boats. The sailors and their sailing yachts were sent out so quickly the grey paint was still wet when they left the docks.