September 12, 1624 - The first practical submarine was demonstrated to England’s King James I and several thousand Londoners. Cornelis Jacobszoon Drebbel (1572 – 7 November 1633) was a Dutch chemist, engineer, and inventor. He designed and built the first prototype submarine in 1620 while working for the English Royal Navy. His design was steerable with a leather-covered wooden frame and powered by oars operated through a leather seal. Between 1620 and 1624, Drebbel successfully built and tested two more prototypes, each one bigger than the last. The final (third) model had 6 oars on each side and could carry 16 passengers in total.
The somewhat sketchy records from the time state the submarine stayed submerged for three hours and could travel from Westminster to Greenwich and back (13.4 miles total), cruising at a depth between 12 and 15 feet (4 to 5 meters). Many times, the submarine attracted crowds to the Thames when it was tested. Air was supplied by snorkel-like tubes that were held above the water's surface by floatation devices, enabling the submarine to be underwater for long periods. Under the rowers' seats were large pigskin bladders, connected by pipes to the outside. A rope was used to tie off the empty bladders; in order to dive, the rope was untied and the bladders filled. To surface the crew squashed the bladders flat, squeezing out the water.
Some reports of the time suggest that King James I actually rode in the third submarine on a trip under the Thames in 1626. Though seeming to have the ear and favor of the King, Van Drebbel's invention failed to interest the British Navy despite a development period of 15 years, Drebbels' submarine never got beyond the trials stage. Ironically, three hundred years later, the submarine would become the most feared of all naval vessels.
Sources: Wikipedia and New Atlas.