Leonardo da Vinci proposed a double hull as a protective feature for ships.
His maritime designs included the idea of placing one hull within another, creating an additional layer between the vessel’s interior and the water. The concept was intended to improve resistance to damage and help keep a ship afloat if its outer surface were breached.
A double hull is not the same as an ironclad ship, which relies on metal armor, or a watertight bulkhead, which divides the inside of a vessel into sealed compartments. Leonardo’s proposal belongs to a broader group of naval ideas in his notebooks, including designs for boats, paddles, and underwater equipment.
Modern ships use double-hull construction for specific safety purposes, especially oil tankers, but that later engineering should not be credited directly to Leonardo. His Renaissance sketch was an early conceptual proposal rather than a tested modern shipbuilding standard. The design shows his habit of applying layered structures to solve problems of impact and buoyancy.