The waterline is the line where the hull intersects the water surface, which indicates the draft of the ship. The change of water temperature will affect the draft of the ship, because the density of warm water is less than that of cold water, so the buoyancy is also small. Similarly, the density of fresh water is lower than that of salinization or seawater, which has the same effect on reducing buoyancy.
- Chinese name
- Waterline
- Foreign name
- Plimsoll line
- Interpretation
- Usually refers to summer Load line
- Represent
- Represented by S
Plimoll line (Plimoll mark) Waterline (waterline mark), usually in summer Load line , denoted by S (there are two kinds of waterline marks in China and internationally). There will be paint marks on the side of the merchant ship to indicate the possible draught of the ship after loading, usually including tropical fresh water, fresh water, tropical sea water, summer sea water, winter sea water and winter North Atlantic water (for ships less than 100 meters in length). The load line is usually accompanied by a circle cut in half by a horizontal line. The horizontal line indicates the status of non shipment in summer, and the letters indicate that Classification Society Name (e.g. L R Lloyd's Register ）。 Load line The name was named in memory of Samuel Plimsoll (1824-1898), a British MP who was committed to promoting the safety of British merchant ships. See Load lines and Load line zone. In practice shipping If the ship sails from low-density waters to high-density waters, and the buoyancy is constant due to the constant gravity of the ship, the drainage volume of the ship will be reduced, which means that the ship will float up and the draft will be reduced. 
