Leonardo da Vinci’s double hull was a ship design with two layers intended to improve protection against leaks.
Leonardo’s notebooks contain proposals for vessels with an inner and outer hull. The space between the layers could help prevent a puncture in the outer skin from immediately flooding the main interior. This is the same broad structural idea later used in some modern ships, although Leonardo’s drawing was an early concept rather than a standardized construction method.
The design reflects his practical interest in naval engineering, especially ship safety and water transport. A double hull can also create a protected compartment around cargo or machinery, but it adds weight, complexity, and construction demands.
Leonardo did not invent every component of shipbuilding, and the surviving sketch should not be confused with a modern tanker’s regulated double-bottom or double-side system. Its historical importance lies in recognizing that separated layers could provide redundancy and protection.