Leonardo da Vinci sketched a double hull as a ship-protection design.
The concept placed a second layer of planking or structure inside the outer hull. This arrangement could help a vessel remain afloat if the exterior suffered damage, although Leonardo’s surviving drawings do not represent a completed, tested ship.
Leonardo investigated many naval ideas during the Renaissance, including pumps, paddle mechanisms, canals, and vessels intended for military use. His notes often combine practical observations with speculative engineering, so a sketch should not be treated as proof that he built the device.
A double hull is also associated with modern tankers and passenger ships, but those later designs use contemporary materials, compartments, and safety standards. Leonardo’s proposal was an early conceptual example rather than the direct operational ancestor of every modern double-hull vessel.