It is usual to base references to deadweight on what can be carried when loaded to ‘summer marks‘ – a vessel’s ‘summer deadweight‘ (occasionally expressed as ‘summer freeboard‘) -all of which expressions can be found under the heading of ‘Load lines’ hereunder. It is important to understand that when a dwcc is quoted this is usually also based on summer marks and a full quantity of bunkers etc. In practice the dwcc is infinitely variable depending on the weight of bunkers and spares and fresh water on board. Consideration also has to be given to any waste oil and water the ship is carrying since in most parts of the world these can no longer be dumped at sea with impunity. Load Lines may be referred to as ‘Plimsoll marks’ or ‘Plimsoll Lines‘, after the British politician Samuel Plimsoll who, in the late nineteenth century campaigned against shipowners who loaded their ships to a depth which endangered seamen’s lives. Eventually, in 1890, a system of calculating and marking a safe ‘freeboard‘ (the distance from the water line to the weatherdeck) was devised and adopted in the United Kingdom, although it was not until 1930 that this finally became international law. A drawing of the actual ‘marks’ is shown below and it will be seen that there are, in fact, six ‘load lines’. This is because account is taken of the world’s geography and weather conditions in assessing the hazards of any particular voyage, as well as whether a ship is transiting a salt or, technically safer, fresh water area. The actual load line mark (the disc with a line through it) lines up with the summer load line referred to earlier. On this mark you will see the letters ‘A’ and ‘B’. These relate to the classification society which surveyed the ship to determine the positioning of her marks and thereafter arranged for them to be ‘cut-in’ and painted on the side of the hull on behalf of the nation in which a ship is registered. In this case the ‘AB’ stands for ‘American Bureau’, but there are many classification societies in the world and, from these, common letters that might be seen could be LR (for Lloyd’s Register), BV (Bureau Veritas), NV (den Norske Veritas), GL (Germanischer Lloyd), and so on.