Waterline length

This measure is significant in determining several of a vessel's properties, such as how much water it displaces, where the bow and stern waves occur, hull speed, amount of bottom-paint needed, etc.

Greater beam and draft produces a larger wetted surface, thereby causing higher hull drag.

In particular, any "displacement" or non-planing boat requires much greater power to accelerate beyond its hull speed, which is determined by the length of the waterline, and can be calculated using the formula: Vmax (in knots) = square root of LWL (in feet) x 1.34.

To get around this rule, designers in the early 20th century began building racing sailboats with long overhangs fore and aft.

The first recorded use of a line (documented by New Jersey marine museum) is by the small and rather unknown naval fleet of Thomas Jefferson.