3. Le Plongeur
Le Plongeur, or “The Diver” got its name from the fact that it represented the very first submarines to use mechanical power. This French-made sea craft by Simeon Bourgeois and Charles Brun (both naval officers) used a piston engine powered by compressed air instead of the regular hand mills. It measured 140 feet long and supplied its crewmen with oxygen from the same air reservoir used to propel its engine. The Diver, or Le Plongeur as it was known, made several successful dives but was eventually taken out of active duty in 1872 because of its limited air supply and dangerous, unstable structure.