Leonardo da Vinci proposed a double hull to reduce flooding after a ship’s outer hull was damaged.
A double hull places a second layer inside or around the main outer shell, leaving a space between the surfaces. If the outer skin is breached, the inner layer can preserve a watertight compartment and delay the entry of water. Leonardo explored this idea in connection with naval engineering.
The proposal was part of his wider interest in ships, canals, hydraulics, and military technology. It should not be read as a complete modern shipbuilding specification: Renaissance materials and construction methods differed greatly from those used in steel vessels today.
The principle later became important in many kinds of ships, including tankers and passenger vessels, although modern double-hull requirements arose from much later engineering and maritime regulation. Leonardo therefore anticipated a useful structural concept, but he did not create the complete modern naval system associated with it.