What propulsion device did Leonardo da Vinci sketch for a paddle boat?

Leonardo da Vinci sketched paddle wheels as the propulsion device for a paddle boat.

In Leonardo’s boat design, rotating wheels fitted with paddles would push against the water and move the vessel forward. The arrangement anticipated a principle later used by paddle steamers, although Leonardo’s proposal was powered by human-operated mechanisms rather than a steam engine.

Leonardo studied watercraft and hydraulic engineering extensively. His notebooks contain designs for boats, canal equipment, pumps, and other machines that converted rotary motion into useful work. The paddle-boat concept shows his interest in reducing dependence on wind and making a vessel’s movement more controllable.

The design is not the same as a modern paddle steamer. Steam-powered paddle boats appeared centuries later, and Leonardo’s sketch does not provide evidence that he built a full-size working vessel. The important feature in the question is the external paddled wheels that drive the boat through the water.