Leonardo da Vinci proposed a double hull, a shipbuilding feature intended to improve safety if one side of a vessel was damaged.
A double hull places an additional layer of structure inside the outer hull, creating a space between them. If the outer skin is breached, the inner hull can help keep water away from the vessel’s interior. Leonardo’s notebooks contain ideas for strengthening ships and separating hull structures, although the precise purpose and implementation of every sketch are not certain.
The principle later became important in naval architecture. Modern tankers use double hulls to reduce the chance that a collision or grounding will open cargo tanks directly to the sea. Other vessels may use internal watertight divisions and protective spaces for related safety purposes.
Leonardo did not invent the modern tanker double hull, and his drawing was not a tested contemporary standard. His proposal is best understood as an early documented exploration of layered ship construction and damage protection.