How does a plimsoll line relate to water?

A load line is a line that limits the maximum mean draft, so that there will be sufficient freeboard and reserve buoyancy to insure the safety of the vessel.

Plimsoll marks consist of a disk with a horizontal line through its center, indicating the summer load line, and a series of other horizontal lines indicating the load lines for various water and seasons.

F or FW---Freshwater.

IS---Indian ocean in summer.

WNA--North Atlantic in winter.

S---Summer in waters other than Indian Ocean.

W---Winter in Waters other than North Atlantic.

T---Tropical waters.

TF---Tropical Fresh water.