It was the first submarine capable of independent underwater operation and movement, and the first to use screws for propulsion.[17] However, according to British naval historian Richard Compton-Hall, the problems of achieving neutral buoyancy would have rendered the vertical propeller of the Turtle useless. The route that Turtle had to take to attack its intended target, HMS Eagle, was slightly across the tidal stream which would, in all probability, have resulted in Ezra Lee becoming exhausted.[18] There are also no British records of an attack by a submarine during the war. In the face of these and other problems, Compton-Hall suggests that the entire story around the Turtle was fabricated as disinformation and morale-boosting propaganda, and that if Ezra Lee did carry out an attack, it was in a covered rowing boat rather than in Turtle.