Leonardo da Vinci proposed a double hull as an armored watercraft feature intended to help a ship remain afloat after damage.
His naval notes included a vessel protected by an outer shell and an inner hull, with space between them. The arrangement would add structural protection and could reduce the chance that a breach in the outside skin would immediately flood the ship’s main interior. Leonardo also considered reinforced forms for military vessels.
A double hull is not the same as a watertight bulkhead. A bulkhead divides the interior of a ship into compartments, while a double hull creates a second outer layer around the vessel. Modern tankers and some other ships use double-hull construction for safety, especially to reduce oil spills after collisions or groundings.
Leonardo’s proposal was a design concept, not a documented working ship. Its importance lies in recognizing that layered protection could improve survivability at sea, centuries before naval engineering adopted comparable arrangements widely.