What ship design did Leonardo da Vinci propose with two parallel hulls joined by a deck?

Leonardo da Vinci proposed a double-hulled ship with two parallel hulls joined by a deck.

The design belongs to Leonardo’s wide-ranging studies of boats and naval engineering. Separating the vessel into two hulls could improve stability and create a broad platform, while the central structure could connect the hulls and support cargo or equipment. The concept resembles the basic arrangement later known as a catamaran.

Leonardo’s notebooks contain many proposed machines rather than tested prototypes. His double-hulled ship should therefore be understood as an engineering study, not as proof that he launched a modern catamaran. He investigated hull shapes, propulsion, water resistance, and methods for moving boats through canals and rivers.

The design is also distinct from a trimaran, which has three hulls. The defining feature here is the pair of parallel hulls. Modern catamarans use the same broad principle, although their materials, hydrodynamics, and propulsion systems are far more advanced.