The Corsair Fleet

A little over looked part of U.S. Coast Guard history is the "Corsair Fleet" that operated out of the Boston Naval Annex. They used sloops and yachts to perform picket and submarine watch duty. They were not motorized so they were well suited for listening for underwater activity. These were operated by Coast Guard reservists.  They were weren't armed with more than submachine guns.  Used primarily during the early stages of the war. Using hydrophones they would listen and track submarines. If one was detected they would track it and call in aircraft and surface craft to hunt down the enemy sub.