Little-known fact: the first submarine and underwater time bomb were created during the American Revolution–before electricity, and before Jules Verne.
It was 100% human-operated (no engines just hand cranks and foot pedals) and used phosphorescent moss as the interior light source because a candle would use up too much of the available oxygen. Even though the "Turtle" failed to complete its few missions and its inventor always felt that he was a failure for it, he is often credited with being the Father of Submarine Warfare.
The son of a Connecticut farmer, David Bushnell was a brilliant man who had to delay going to college until he was 31 years old. While he was studying at Yale, he proved that gunpowder could be exploded underwater and also created a timing device to allow for delayed detonation–the first underwater time bomb.
His last year at Yale coincided with the beginnings of the American Revolution. The university temporarily closed due to the impending crisis of war, but Bushnell knew he could use an underwater explosive to help his fellow patriots fight the superior British military power if only he could find a way to deliver it to the target. He knew the machine had to be able to be completely submerged for at least a short amount of time to avoid detection and be maneuvered in the water.
His design is simple and efficient: a small barrel-like vessel, almost like two turtle shells glued together with simple pedal powered propellers. It had to be able to deliver the underwater time bomb, attach it to the target ship's hull, and then retreat before the bomb detonated, all before the pilot ran out of oxygen and had to surface.
The Connecticut River Museum has both a cut away display that you can sit in and feel what it was actually like to be inside the Turtle and a full scale replica that was hand made for the 1976 bicentennial. They tested the machine in a nearby harbor, and it is said to have worked beautifully.