A load line is one of a number of lines painted on the sides of a ship which show the maximum depths to which the ship may be immersed when arriving at, sailing through or putting to sea in the different load line zones. The positioning of these lines is determined by the rules agreed at the International Conference on Load Lines which has been ratified by many maritime countries. The zones are geographical areas, defined by the International Conference on Load Lines. There are five types of zone: tropical zone, summer zone, winter zone, seasonal tropical zone and seasonal winter zone.The first three types of zone are permanent, that is, the one appropriate load line applies all year round. The last two zones are seasonal and the corresponding load lines apply at certain periods only, depending on the particular zone; for the rest of the year in these seasonal zones, the summer load line applies.