Leonardo da Vinci proposed a double hull to help keep a damaged ship afloat.
A double hull places an additional layer of structure inside or alongside the outer hull. If the outside is breached, the inner layer can limit the spread of water and preserve buoyancy. Leonardo included related shipbuilding ideas in his notebooks while studying naval engineering and the movement of water.
The concept was not a modern steel tanker design. Renaissance ships used different materials, construction methods, and compartment arrangements, and Leonardo’s proposal was never documented as a standardized shipbuilding system.
Double hulls later became important in several kinds of vessels, including certain modern tankers and passenger ships. Their purpose is often misunderstood: a second hull improves protection against some collisions or groundings, but it does not make a vessel impossible to sink.