Length on the Waterline (LWL)

The fore-and-aft length of a vessel’s hull at the water surface for a stated loading and attitude.

LWL is measured between the forward and after intersections of the hull with the specified waterline. It changes with displacement and trim and, on overhanging hulls, can increase as the vessel heels or settles into a wave.

The value influences displacement-hull resistance and is used in several design ratios, but it is not the same as length overall or a fixed legal length. The reference loading condition and measurement convention must accompany any precise comparison.