Leonardo da Vinci proposed a double hull to reduce flooding inside a ship.
His ship designs included an inner and outer hull separated by a space. The arrangement was intended to protect the vessel if the outer skin was damaged and to limit the amount of water entering the main interior. Leonardo’s notebooks contain many studies of boats, canals, locks, and hydraulic engineering.
A double hull is not the same as a watertight compartment system, although both can improve survivability. Modern double-hulled ships place a second layer around parts of the hull, while bulkheads divide a ship’s interior into separate compartments. Leonardo’s proposal belongs to a much earlier period than modern steel shipbuilding.
Double-hull construction later became especially important for oil tankers. International maritime rules expanded its use after major tanker accidents, because a second hull can reduce the chance that a collision or grounding immediately releases cargo into the sea.