Leonardo da Vinci recommended a double hull as a way to reduce the risk of flooding after a ship’s outer skin was damaged.
A double hull places a second watertight layer inside the outer hull, leaving a space between them. If the exterior is pierced, the inner layer can keep water away from the ship’s main compartments. This principle is straightforward today, but it was an advanced idea in Leonardo’s studies of vessels and naval engineering.
Leonardo’s notebooks contain many investigations of water, boats, locks, and hydraulic machines. His ship-related designs were generally exploratory studies rather than a single completed shipbuilding program. The double-hull concept later became important in modern ship construction, especially for oil tankers and other vessels where containment and damage protection matter.
A double hull is not the same as a double-ended ship or a raised deck. Its defining feature is the second protective shell below or alongside the primary hull.