Leonardo da Vinci sketched a boat propelled by paddle wheels.
In Leonardo’s design, rotating wheels fitted with paddles would push against the water and drive the boat forward. The mechanism transferred rotary motion from a human-powered system to the wheels, offering an alternative to ordinary rowing or sailing. His notebooks contain several studies of watercraft and mechanical power transmission.
The idea is a paddle-wheel propulsion system, not a steam engine. Paddle wheels were later used widely on boats, especially after steam power made continuous rotation practical, but Leonardo’s sketch predates the industrial steamship era by centuries. His proposal should therefore be treated as an early mechanical concept rather than a modern powered vessel.
Leonardo also studied canals, locks, pumps, and water flow. Those subjects were closely connected: better control of water and mechanical motion could improve transport, construction, and military engineering.