Leonardo da Vinci proposed a double hull to reduce flooding after a ship’s outer hull was damaged.
A double-hull design places a second layer inside the outer shell of a vessel, leaving a space between the two layers. If the outside is pierced, the inner layer can help keep water away from the ship’s main compartments. Leonardo included this principle among his maritime engineering ideas.
The concept was centuries ahead of the widespread use of double hulls in modern ships. Today, double-hull construction is especially associated with tankers, where the extra layer helps reduce the chance of cargo escaping after a collision or grounding.
Leonardo’s proposal should not be confused with a double-deck ship or a ship with two separate hulls, such as a catamaran. In his design, the key feature was an inner protective shell within the same vessel.