Which U.S President commanded a submarine?

No U.S. President has ever commanded a submarine. President Carter was a submarine officer with command aspirations, but he failed his Engineer Officer interview with then-Admiral Hyman G. Rickover, which essentially ended his career aspirations. Kennedy was a PT boat skipper in the Pacific, and George Bush Sr. was a Navy TBM Avenger pilot in the Pacific. Presidents Johnson, Nixon, and Ford were all Naval officers, but weren't in the submarine force.