Leonardo da Vinci designed a paddle wheel as a human-powered device to make a boat move against the current.
Leonardo’s notebooks contain designs for boats driven by rotating wheels fitted with paddles. Operators would turn mechanisms that transferred human effort to the wheels, pushing water backward and moving the vessel forward. The idea belongs to his broad studies of machines, water power, and transport.
A paddle wheel works by presenting broad blades to the water. As the wheel turns, the blades produce thrust, much as oars do, but in a continuous rotary motion. The arrangement is therefore different from a screw propeller, which Leonardo also studied in other contexts.
Leonardo’s boat designs were proposals rather than documented working vessels. Practical paddle-wheel boats became important much later, especially after steam engines supplied continuous power. His sketches nevertheless show an early attempt to replace intermittent rowing with a mechanical rotary drive.