Leonardo da Vinci proposed a double hull as a protective ship design with two layers separated by a space.
The concept appears among his studies of naval engineering and ship construction. A second hull could make a vessel more resistant to damage from collisions or underwater impacts, because the outer layer could be breached without immediately flooding the inner compartment. The idea anticipates a principle later used in naval architecture and modern tankers.
Leonardo did not invent the modern steel double-hull tanker, and his drawing was a design study rather than a documented working ship. The double hull is also different from a watertight subdivision system, which uses internal bulkheads to divide a single hull into compartments. Modern maritime rules eventually required double hulls for many oil tankers, especially after environmental concerns about spills.