The load line is the deepest allowable condition of load. For trimmed vessels, this should be taken at the equivalent displacement as the load line at level trim. Load lines may be set by convention (see international convention on load lines), or set to a lower draught as per request (see stability conditions).
The load line is denoted with a plimsoll mark on the hull on convention ships.
The load line may be exceeded only in certain special cases. If it can be shown that a vessel loaded in freshwater will not exceed it's load line in saltwater, it may be allowed to submerge the load line/plimsoll mark (see freshwater allowance). Similarly, in brackish waters, a dockwater allowance may be taken for the difference in specific gravities. Vessels loading in protected waters may also be allowed to overload the equivalent of the fuel burn to saltwater, representing the relative safety of rivers to oceans. This latter allowance generally excludes inland seas, such as the great lakes.