up. The boat was built by prisoners in  McNeil Island in Washington for this specific purpose, and was used  for much of the time Alcatraz was in service as a prison. The makers  of the movie borrowed the Johnston from the Sea Scout crew who was  operating her at the time (Sea Scout Ship #145, based in Redwood  City, CA). Gary Warren (qv), who is listed in the credits as a  guard, was in fact the boat operator, and was also the leader of the  Scout crew at the time.