Leonardo da Vinci proposed a double hull by placing two ship hulls one inside the other for added protection.
His shipbuilding studies included ideas for making vessels safer against collision and damage. A second layer between the outside of the ship and its inner structure could provide a buffer, helping limit the spread of water after a breach. The principle resembles the double-hull construction later used in some ships and marine vessels.
Leonardo’s notebooks contain many ship and water-engineering ideas, but the surviving drawings do not establish that he built or tested a full-size double-hulled ship. His proposal should therefore be treated as an early conceptual design rather than a demonstrated invention.
Modern double hulls serve several purposes, including structural protection and reducing the chance that a collision will rupture an inner tank. In oil tankers, international rules later made double-hull construction an important safety requirement.