The hull is the watertight body of a ship or boat. Atop the hull may be a deckhouse or some other form of superstructure, like a mast. The line where the hull meets the water surface is called the waterline.
The structure of the hull varies depending on the vessel type. In a typical modern steel ship, the structure consists of watertight and non-tight decks, major transverse and watertight (and also sometimes non-tight or longitudinal) members called bulkheads, intermediate members such as girders, stringe