Leonardo da Vinci proposed a double hull as a ship construction intended to reduce the risk of sinking.
A double hull places a second watertight layer inside or alongside the outer hull. If the outside is breached, the inner layer can keep water from immediately reaching the main interior spaces. Leonardo explored this principle in his naval and engineering studies.
The idea was not a complete modern shipbuilding system, and Leonardo’s notebooks contain proposals rather than evidence of a working vessel built to those specifications. His interest arose from the practical dangers of maritime travel and military naval operations.
Modern double-hull construction is especially associated with oil tankers and some other vessels, where the space between hulls can help protect cargo tanks from collision damage. Leonardo’s proposal is therefore an early example of a safety principle later used in large-scale ship design.