The vision of a manned submersible exploring the ocean deeps is an old one. In 332 BC, Alexander the Great is reported to have descended into the Aegean Sea in a glass sphere to observe aquatic life. In the early 16th century, Leonardo da Vinci sketched plans for a theoretical submarine, as he had for a functioning helicopter. The first realisable submarine schematic, devised by William Bourne in 1578, inspired the Dutch designer Cornelis Drebbel, who in the early 17th century secured the interest and funding of King James I of England to construct a prototype. In 1623, Drebbel’s submersible, using leather goatskin bags to vent water, made its erratic passage along the River Thames from Westminster to Greenwich.
All of these inventions were bold ideas ahead of their time, but the submarine as commonly understood – that is, not a simple bathysphere lowered into the ocean and pulled back up again but a self-propelling undersea vehicle – was mainly a theoretical exercise until the use of David Bushnell’s Turtle submersible by American Revolutionary forces in 1776. The first ‘submarine’ to be deployed in combat, the Turtle used water as ballast and a screw propeller at its rear, both methods still in use today. Although it failed in its attempted missions to attach explosives to the undersides of British warships, the Turtle put down a marker for the future of warfare.
That future arrived in the form of the ‘plunging boat’ Nautilus, widely considered the first practical submarine ever constructed. Designed between 1793 and 1797 for the French First Republic, it was the brainchild of the American engineer Robert Fulton, inventor of the first commercially successful steamboat. Built of copper sheets attached to iron ribs, on which sat two horizontal diving pins to control the angle of descent, the Nautilus was propelled by a hand-cranked screw propeller. In trials at Le Havre harbour in 1801, Fulton took the Nautilus down 7.6m (25 ft) and stayed submerged for an hour.
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