What thewhite line is called on the side of a ship?

The lines drawn around the hull of a ship near the water-line is called a "Plimsoll line". This horizontal line is easily seen when the ship is empty and therefore riding higher out of the water. The more cargo loaded into ship the deeper it sinks into the water, and a ship can only be loaded with cargo etc down to this line and no furthur. Before its introduction there was no safe-loading-line on a vessel to prevent overloading by unscrupulous owners.