The F/V Spray was a fishing vessel out of Boston, Massachusetts in the early 20th century. The US Navy purchased her to be used as a decoy against Confederate commerce raiders. While underway, she would tow an underwater submersible. If attacked by a raider, she would notify the submersible via a telephone line on the tow and the sub would slip off to attack the raider.
The notion was by Patrick O'Donnell, a fishing boat captain and ex navy man, who had been captured by such a raider then exchanged. He convinced the Navy of the idea and so he and some of his fishing crew along with some naval sailors undertook the project. They had some initial success attracting the attention of a Confederate submersible which was torpedoed and sunk by the USS Bluefin. The crew of the Spray rescued three survivors, including the captain, Senior Lieutenant Ralph Briggs.
However, this success brought widespread publicity making Confederate forces much more cautious with only one more successful sinking on the West Coast early in the program. The US Navy decided to cancel the program and reassigned the crew (including the fishermen since they were required to enlist for the duration) to other ships.