The waterline is a line, either real or imaginary, on the side of a ship representing the level the water reaches when the ship is at sea.
Ray painted below the waterline with a special anti-rust paint.
waterline in British English
(ˈwɔːtəˌlaɪn)
noun
1.
a line marked at the level around a vessel's hull to which the vessel will be immersed when afloat
2.
a line marking the level reached by a body of water
waterline in American English
(ˈwɔtərˌlaɪn)
noun
1.
the line to which the surface of the water comes on the side of a ship or boat
2.
any of several lines parallel to this, marked at various heights on the hull of a ship, indicating the various degrees of submergence when the ship is fully or partly loaded, or unloaded, and on an even keel
3. US
a pipe, tube, or other line connected to a source of water
4.
watermark (sense 1)
Examples of 'waterline' in a sentence
waterline
The only reason they're thought to have survived the French bombardment was because they'd been built below the waterline.
MacNeill, Alastair CODE BREAKER (1994)
When we reached the beach at last, Trevor threw his bicycle to the ground and rushed to the waterline with his bag of bread.
Hodgman, Ann MY BABYSITTER HAS FANGS (1994)
Tell him to put at least two shells through the waterline so she sinks quick.
Terman, Douglas CORMORANT (1994)
For three generations she remained on view until finally she either rotted away or burned to the waterline.