What type of ship propulsion did Leonardo da Vinci study using paddle wheels?

Leonardo da Vinci studied paddle-wheel propulsion for moving boats through water.

His notebooks contain designs in which rotating wheels fitted with paddles push against the water and create forward motion. The mechanism could be driven by people turning cranks, linking human power to a repeatable rotary movement. Leonardo examined the arrangement as part of his broader work on boats, canals and hydraulic machines.

Paddle wheels were not powered by steam in Leonardo’s designs. Steam engines capable of practical marine propulsion appeared much later, especially in the eighteenth and nineteenth centuries. Leonardo’s proposals therefore belong to the history of mechanically driven boats, not to the steamship era.

The drawings also should not be confused with modern propeller propulsion. A paddle wheel pushes water with broad blades rotating at the surface or beside the hull, while a screw propeller operates beneath the water. Leonardo’s studies show his effort to replace or supplement sails with controlled mechanical power, although there is no firm evidence that his exact boat was built.