Definition - What does Waterline mean?
A waterline is defined as a line or an interface formed between the water and a body lying in it. In other words, a waterline can also be defined as the line formed by the topmost layer of water that just touches the body of any object floating on the water.
A waterline terminology is primarily associated with marine ships, tankers, submarines and other vessels that float on the water. On the ships, large vessels, tankers, floating barge or any other structure floating in water, a waterline is represented by a plimsoll line.
Corrosionpedia explains Waterline
In marine terminology, the waterline is the line where the hull of the ship just touches the surface of the water. This water line is called as a plimsoll line or the international cargo loading line on the ships during transportation which indicates the draft of the ship. It also indicates the legal limit to which a ship may be loaded for specific water types and temperatures to safely maintain good amount of buoyancy with cargo on board and ship or vessels floats risk free with complete control.
Temperature affects the waterline level because when water is warm it will be less dense when compared to the cold water and thus provides less buoyancy to the floating object. This is the same condition faced in the saline water of sea when compared to the fresh water of lakes or rivers.
For vessels with displacement hulls, the hull speed is determined by the waterline length however, in a sailing boat, the waterline length can change significantly as the boat heels, and can dynamically affect the speed of the boat.
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