Leonardo da Vinci proposed a double hull to help protect ships from damage and flooding.
A double hull places an additional layer of structure inside or alongside the outer hull, creating a space between the two shells. If the exterior is breached, the inner layer can help preserve buoyancy and keep water from immediately reaching the vessel’s main interior spaces.
Leonardo explored the idea in the context of ship design and naval engineering. His proposal predates the widespread use of double-hull construction in modern ships by centuries, although later shipbuilders developed the concept in different forms and for different purposes.
A double hull is not the same as a double-ended ship or a ballast tank. The defining feature is the second protective hull layer. Leonardo’s design demonstrates his interest in preventing failure rather than merely repairing damage after it occurred.