WATERLINE

n. line indicating how high water has reached on the side of a ship; water level, watermark

Waterline refers to an imaginary line marking the level at which ship or boat floats in the water. To an observer on the ship the water appears to rise or fall against the hull . Temperature also affects the level because warm water provides less buoyancy, being less dense than cold water. Likewise the salinity of the water affects the level, fresh water being less dense than salty seawater.
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Noun
1. a line corresponding to the surface of the water when the vessel is afloat on an even keel; often painted on the hull of a ship
(synonym) water line, water level
(hypernym) line
(hyponym) load line, Plimsoll line, Plimsoll mark, Plimsoll

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