Leonardo da Vinci proposed a double hull to improve a ship’s resistance to flooding.
His naval studies included dividing a vessel’s interior into separate compartments. If one part of the hull were damaged, the separation could limit the spread of water and help keep the ship afloat. This is the same general safety principle later used in watertight subdivision and double-hull construction.
Leonardo’s proposal belongs to a wider group of naval and hydraulic ideas in his notebooks. It was not a complete modern shipbuilding standard, and the exact arrangement in surviving drawings should not be confused with every contemporary use of the term double hull. Modern double-hull ships have an inner hull separated from an outer hull by a space, especially in tanker construction.
The design is notable because it applies compartmentalization to maritime safety. Leonardo made similar use of separation and controlled flow in other engineering studies, but the surviving evidence supports calling this a proposal rather than a documented ship that he built.