The ability to remain and travel underwater for an extended period of time has long been a dream for a good portion of mankind, perhaps second only to that of flying. The first “submersible” may have been a kind of glass container made for Alexander the Great so that he could observe undersea life firsthand. Despite this early attempt, fate decreed the idea of traveling beneath the surface of the water would lie fallow for nearly another 2,000 years after this experiment in about 332 B.C. Alexander’s death the next year effectively squashed any further developments.

While people often tend to think of submarines as a modern invention, inventors created several prototypes from 1580 onward, and they even attempted to use them. Some of the designs remained theoretical and never got off the drawing board, but as time went on, several Europeans built and tested primitive submarines. Most of these early subs were made of wood and often possessed an awkward shape, but a French priest first proposed the now familiar cylindrical layout in 1634. He determined that this shape would make it easier for the submarine to withstand water pressure, while likewise improving maneuverability.

The potential for submarines to be used in warfare came to the fore very quickly. The “Rotterdam Boat” appears in history as the first submersible to be used for this purpose, built in 1634 for the express mission of attacking British vessels in the Thames. However, the mechanism intended to propel the boat proved so weak that it went nowhere at all, and merely sank.

Propulsion proved a major obstacle for early submarines. David Bushnell encountered this problem when he built a submarine in 1776 with the intention of drilling holes in the hulls of British ships during the Revolutionary War.