Hull
The Hull is the main watertight body of a ship or boat — the structure that provides buoyancy, strength and the form that moves through the water. It comprises the shell plating, the internal framing (frames, girders, floors), the keel at the bottom, the decks, and the bulkheads that divide it into compartments.
The hull's design governs a vessel's speed, fuel efficiency, stability, cargo capacity and seakeeping, and it must be strong enough to withstand the sea's forces and the loads of cargo. Its underwater form and cleanliness directly affect resistance and fuel consumption (hence hull cleaning and coatings). Structurally, the hull is protected by watertight subdivision so that flooding in one compartment need not sink the ship. Merchant hulls are increasingly double-hulled (notably tankers, for pollution protection). The hull is the fundamental structure of any vessel, insured under hull & machinery cover and maintained and surveyed throughout the ship's life. It is the ship's body.
The hull is the ship itself — the watertight body that floats, carries the cargo and takes the sea's punishment. Its shape drives speed and fuel use, its subdivision keeps the ship afloat when damaged, and its condition is a constant focus of cleaning, survey and hull-and-machinery insurance. Everything else is built on it.
What is the hull made up of?
Shell plating, internal framing, the keel, decks and the bulkheads that divide it into watertight compartments.
Why does hull form matter?
It governs speed, fuel efficiency, stability, capacity and seakeeping; a fouled or damaged hull raises resistance and fuel use.