waterline vs load line

waterline and load line both are nouns.

Word	Noun	Adjective	Verb	Adverb
waterline	Yes	No	No	No
load line	Yes	No	No	No

As nouns, load line is a hyponym of waterline; that is, load line is a word with a more specific, narrower meaning than waterline:

waterline: 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
load line: waterlines to show the level the water should reach when the ship is properly loaded

Other hyponyms of waterline include Plimsoll, Plimsoll line, Plimsoll mark.

waterline (noun)	load line (noun)
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	waterlines to show the level the water should reach when the ship is properly loaded