Leonardo da Vinci sketched a double-hull system that placed an additional layer inside a ship’s outer hull.
The concept appears among Leonardo’s naval and engineering studies. A second hull could help protect a vessel from damage and reduce the chance that water would immediately enter the main interior. Leonardo’s broader notebooks show sustained interest in shipbuilding, waterways, pumps, locks, and military engineering.
A double hull is not the same as a catamaran. A catamaran has two separate parallel hulls, while a double-hull vessel has an inner and outer shell around the same central hull volume. Modern tankers often use double hulls to reduce pollution after collisions or groundings, but those ships use materials, compartmentalization, and regulations unavailable to Leonardo.
Leonardo’s sketch was an early conceptual contribution rather than a documented working ship. Its value lies in recognizing layered protection as a way to improve maritime safety.