In terms of these load line rules, ships are required to ensure that the correct load line mark is displayed with respect to her midship draught, appropriate to the load line zone that she is sailing through. The chart on the next page illustrates these zones.

Although the International Load Line Rules, as the title implies, are in force 'internationally', there have been a number of misinterpretations of these rules experienced when ships call at South African ports.

Many ship masters believe that it is permissible to submerge their vessel's Load Line marks in salt water, provided they can show that the vessel's displacement does not exceed that which is laid down on the vessel's load line certificate. In other words, they believe that even if the ship is 'sagged', provided that the load displacement for the load line zone within which the ship is operating, is not exceeded, then the vessel is not considered 'overloaded'.