Leonardo da Vinci proposed a double hull to reduce damage from collisions.
The concept used two layers of the boat’s outer structure, creating a protective arrangement around the vessel. If the outer layer were damaged, the inner hull could help keep water from entering the main interior. The idea resembles a principle later used in some shipbuilding and marine engineering.
Leonardo’s notebooks contain many studies of boats, waterways, and naval machines. His designs included both practical transport ideas and military concepts, reflecting the importance of rivers, canals, and sea power in Renaissance Italy.
A double hull is not the same as a double-ended boat or a catamaran. The term here refers to protective layers forming the vessel’s sides and bottom, not two separate side-by-side hulls. Leonardo’s proposal was a design concept, not a documented shipbuilding project that entered service.