load line vs Plimsoll mark

load line and Plimsoll mark both are nouns.

Word	Noun	Adjective	Verb	Adverb
load line	Yes	No	No	No
Plimsoll mark	Yes	No	No	No

As nouns, load line and Plimsoll mark are synonyms defined as:

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

Other synonyms of load line include Plimsoll, Plimsoll line.

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