What double-hulled ship concept did Leonardo da Vinci propose to reduce the risk of sinking?

Leonardo da Vinci proposed a double-hull ship concept to reduce the risk of sinking.

The idea used an inner hull and an outer hull separated by a space. If the outer skin were damaged, the inner structure could provide additional protection against flooding. Leonardo explored this arrangement in his studies of ships and naval engineering, alongside ideas for pumps, underwater devices, and methods of moving vessels.

A double hull is not the same as a catamaran. A catamaran has two distinct parallel hulls that support a deck, while a double-hull ship has nested layers forming one vessel. Modern tankers and other ships may use double hulls for structural and environmental protection, but their materials, engineering, and regulations are very different from Leonardo’s proposal.

Leonardo’s ship concepts were largely theoretical. His notebooks contain many technically imaginative designs, but surviving drawings do not show that this particular vessel was built or tested in Renaissance Italy.