Leonardo da Vinci proposed a ship-safety system using a double hull.
His maritime sketches include vessels with an inner hull and an outer hull separated by a gap. The purpose was to reduce the danger of water entering the main interior if the outside skin was damaged. This is an early example of a layered marine structure, although Leonardo’s drawing is a design concept rather than evidence of a completed ship.
The principle later became important in shipbuilding, especially for vessels carrying oil. Modern double-hull tankers place a second barrier around the cargo tanks, reducing the chance that a collision or grounding will immediately release oil into the sea. International rules introduced through MARPOL required double hulls for many oil tankers after major pollution disasters.
Leonardo’s proposal should not be confused with a catamaran. A catamaran has two separate parallel hulls that support one deck, whereas a double-hull vessel has a second protective skin around the same main hull or cargo space.