What Leonardo da Vinci invention was a paddle-wheel boat designed to move without conventional oars?

Leonardo da Vinci's paddle-wheel boat was designed to move without conventional oars.

The concept used rotating paddles to push against water and propel the vessel. Leonardo's drawings show how motion from a crank or other mechanical drive could be transferred to paddle wheels mounted beside or beneath a boat. This offered an alternative to rowing and sailing.

Leonardo did not create a modern steam-powered paddle steamer. His design depended on human-powered mechanical operation, and there is no firm evidence that the full vessel was built and tested in his lifetime. Later paddle-wheel boats used engines to supply continuous power.

The idea is also distinct from a propeller-driven boat. Paddle wheels push water with broad blades turning outside the hull, whereas a propeller uses rotating blades arranged around a central shaft, usually beneath the vessel.