What Leonardo da Vinci design used paddles to propel a boat?

Leonardo da Vinci designed a paddle boat that used rotating paddles to propel it through water.

His sketches show a vessel driven by mechanical paddles rather than relying only on oars or wind. Cranks and gears were intended to transfer human effort to the paddle mechanism. The arrangement anticipated the basic principle later used by paddle-wheel boats, in which broad blades push water backward and the vessel moves forward.

Leonardo's design belongs to a group of Renaissance studies of boats, bridges, canals, and water machinery. He was interested in making transport less dependent on wind and in converting rotary motion into useful movement.

The design was not a steam-powered paddle steamer. Steam engines and practical steamboats appeared centuries later. Leonardo's boat depended on people turning or operating its mechanical drive, making it an early conceptual predecessor rather than a modern powered vessel.