Leonardo da Vinci proposed a double hull to help ships survive damage.
A double-hulled vessel has two layers of hull structure separated by a space. If the outer layer is pierced, the inner layer can remain watertight, reducing the chance that the ship will sink immediately.
Leonardo included this idea among his studies of ships and naval engineering. The concept reflects his habit of using separate layers and compartments to improve safety, although the surviving drawings do not represent a modern naval design in every detail.
Double hulls later became important in shipbuilding, especially for tankers and other vessels carrying hazardous liquids. Leonardo should not be credited with creating every later application, but his sketches are an early and recognizable proposal for a protective second hull.