Leonardo da Vinci sketched a double hull as a ship-safety feature intended to reduce flooding after damage.
The concept placed an additional layer inside the outer hull, creating a protected space between the ship’s exterior and its inner structure. If the outside were breached, the second layer could help keep water from reaching the main interior.
Leonardo studied ships, waterways, and naval engineering extensively. His notebooks contain many maritime ideas, including hull forms, pumps, and methods for moving vessels through water. The double-hull principle later became important in modern ship design, especially for oil tankers.
A double hull is not the same as a watertight bulkhead. A bulkhead divides a ship into compartments, while a double hull adds a second shell around part or all of the vessel. Leonardo’s sketch was an early conceptual treatment, not a modern construction standard.