What propulsion method did Leonardo da Vinci include in a boat design?

Leonardo da Vinci included paddle wheels as the propulsion method in one of his boat designs.

His notebooks contain studies of boats and water-powered machinery, including a vessel moved by paddle wheels. Rotating paddles push against the water and produce forward thrust, a principle later used in paddle steamers and other watercraft.

Leonardo’s design was not a steam-powered boat. Renaissance engineers had no compact steam engine comparable to those developed centuries later, so the proposal depended on human or mechanical power to turn the wheels.

The boat studies form part of Leonardo’s broader interest in fluid motion, gearing, and practical transport. They should be understood as engineering concepts recorded in notebooks, not as evidence that he launched a working powered vessel.