Waterline
The waterline is the line where the hull of a ship meets the surface of the water.
A waterline can also refer to any line on a ship's hull that is parallel to the water's surface when the ship is afloat in a level trimmed position. Hence, waterlines are a class of "ships lines" used to denote the shape of a hull in naval architecture lines plans.
The load line (also known as Plimsoll line) is the waterline which indicates the legal limit to which a ship may be loaded for specific water types and temperatures in order to safely maintain buoyancy.
For vessels with displacement hulls, the hull speed is defined by, among other things, the waterline length. In a sailing boat, the waterline length can change significantly as the boat heels, and can dynamically affect the speed of the boat.
Similar Artists