What Leonardo da Vinci vessel concept used paddle wheels to move through water?

Leonardo da Vinci’s vessel concept using paddle wheels to move through water was a paddle-wheel boat.

Leonardo sketched boats fitted with large wheels whose blades would push against the water. Turning the wheels would create forward motion, allowing the vessel to travel without relying entirely on wind or oars. Some versions appear to use human-powered mechanisms, such as cranks connected to the paddle wheels.

The concept shows Leonardo applying rotary motion to water transport. He studied gears, shafts, and mechanical power extensively, and a paddle wheel offered a way to convert movement inside a boat into thrust outside it. The arrangement anticipated a principle later used in powered boats and ships.

Leonardo did not invent the general idea of a paddle wheel; ancient and medieval engineers had explored similar devices. Nor was his design a steamboat, because his sketches do not provide a documented steam engine. The accurate description is a paddle-wheel boat, a mechanically propelled vessel concept.