What two-hulled vessel did Leonardo da Vinci propose to improve stability on water?

Leonardo da Vinci proposed a double-hulled ship, a vessel with two parallel hulls intended to improve stability on water.

Separating the hulls creates a broad base of support and can reduce rolling compared with a single narrow hull. Leonardo explored the arrangement while designing boats and studying ways to move vessels efficiently. The concept resembles the principle later used by catamarans, although Leonardo’s drawing was a Renaissance proposal rather than a modern production design.

The term “double-hulled ship” is more precise here than catamaran. Catamaran is the standard modern name for a particular multihull vessel, while Leonardo’s design is usually discussed as an early conceptual predecessor. The drawing does not establish that he built a working ship of this type.

Leonardo’s naval studies covered hull shapes, propulsion, locks, and defenses. His aim was often to solve a specific practical problem—such as stability or maneuverability—through geometry and mechanical design.