Leonardo da Vinci included a double hull in a proposed ship design as protection against leaks.
Leonardo studied shipbuilding and naval engineering in notebooks that contain ideas for improving vessels. A double hull places an inner hull inside an outer hull, creating a space between them. If the outside skin were damaged, the inner structure could help keep water from immediately flooding the ship.
This concept should not be confused with a modern double-hulled tanker designed primarily for oil-spill prevention. Leonardo’s proposal belongs to an earlier context of wooden ships, manual construction and military engineering. The surviving sketches do not establish that Leonardo built or tested a full-size double-hulled vessel.
The design nevertheless anticipates a principle later used in ship construction. Separate hull layers can provide redundancy, although they also add weight, cost and construction complexity. Leonardo’s naval studies show that his inventions extended beyond flying machines and automata into practical questions about buoyancy, hull strength and maritime safety.