Leonardo da Vinci proposed a double hull by separating a ship's outer and inner hulls.
His maritime studies included the idea of creating a second layer around a vessel, leaving space between the two hulls. Such a structure could help protect the inner hull from damage caused by collisions or impacts.
Leonardo's proposal was centuries ahead of modern double-hull requirements, but it should not be confused with a complete modern tanker design. Contemporary double hulls became especially important in oil transportation because they reduce the chance of cargo escaping after a collision or grounding. Leonardo's notes show the protective principle, not evidence that he built a full-scale double-hulled ship.