Leonardo da Vinci proposed a double hull, a protective naval feature formed by two layers of ship structure.
His maritime studies include ideas for strengthening vessels against impacts and reducing the danger of flooding. A second hull or internal layer could create a protective space between the outside of a ship and its inner compartments. The concept was centuries ahead of the double-hull systems later used in some ships and modern tankers.
Leonardo’s notebooks contain many ship designs, including boats powered by paddles, wheels, or screw-like mechanisms. These drawings were proposals rather than evidence that he constructed a full-scale double-hulled vessel. The precise arrangement in historical sketches should not be confused with every modern engineering use of the term.
Modern double hulls are designed according to detailed structural, stability, and safety rules. In oil tankers, the arrangement became especially important because it reduces the chance that a collision or grounding will immediately breach cargo tanks.