What Leonardo da Vinci invention was a double-hulled boat intended to reduce the risk of sinking?

Leonardo da Vinci designed a double-hulled boat intended to improve stability and reduce the risk of sinking.

The concept used two parallel hulls connected across the top. Separating the buoyant bodies could make the craft more stable than a narrow single hull, while the enclosed arrangement offered additional protection against water entering the vessel.

Leonardo explored many boat and watercraft ideas in his notebooks, including vessels for transport, military use, and engineering work. His drawings were proposals rather than evidence that he built this double-hulled craft at full scale.

The design is sometimes described as an early catamaran concept. A catamaran is defined by two separate hulls joined by a frame or deck, but Leonardo’s sketch should not be treated as the first modern catamaran in a strict historical sense.