Half-hull of the 46-gun ship of the line Tigre, build from 1724 in Toulon after plans by Blaise Coulomb. A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present.The line where the hull meets the water surface is called the waterline. The structure of the hull varies depending on the vessel type.alf-hull of the 46-gun ship of the line Tigre, build from 1724 in Toulon after plans by Blaise Coulomb. A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present.