What Leonardo da Vinci machine used a paddle wheel to move a boat through water?

Leonardo da Vinci designed a paddle-wheel boat to propel a vessel through water.

His sketches show paddle wheels turned by a human-powered mechanism. As the paddles pushed against the water, they would produce forward thrust without relying on wind in a sail. The concept was intended for use on rivers and other relatively calm waterways.

A paddle wheel is not a propeller. A wheel uses broad blades or paddles moving around an axle, while a propeller uses twisted blades rotating on a shaft. Leonardo's design also should not be confused with a modern steamship: his proposed power came from people operating the machinery, not from an engine.

Leonardo made several studies of boats, pumps, locks, and water movement. These drawings reveal an interest in converting rotary motion into useful transport. The paddle-wheel boat was a conceptual machine; there is no firm evidence that Leonardo built and tested a full-scale version.