Hull

The hull is the watertight shell of the boat. Its shape decides almost everything: speed, how the boat goes through waves, stability and comfort. The part under water is also called the underbody; the line where the water meets it at rest is the waterline.

On a modern racing monohull, the hull is wide and flat at the back so it can plane, sliding over the water rather than pushing through it. On a multihull, the central hull and the floats are joined by crossbeams.