Leonardo da Vinci proposed a double hull to improve a boat’s resistance to leaks.
Leonardo’s naval studies included designs with two layers of hull structure. The space between the layers could provide added protection if the outer skin were damaged, reducing the chance that water would immediately reach the vessel’s interior. This is the basic principle behind a double hull.
His work on boats formed part of a wider investigation of water transport, ship design, and naval engineering. Leonardo also studied propulsion, steering, and methods for moving vessels through canals and rivers. The surviving sketches are proposals rather than documentation of a completed ship built to his specifications.
Modern double-hull construction is especially associated with oil tankers and certain passenger or commercial vessels. It is not the same as a catamaran, whose two hulls are separate side-by-side buoyant bodies rather than two enclosing layers around one main hull.