lubber's mark vs lubber line

lubber's mark and lubber line both are nouns.

Word	Noun	Adjective	Verb	Adverb
lubber's mark	Yes	No	No	No
lubber line	Yes	No	No	No

As nouns, lubber's mark and lubber line are synonyms defined as:

lubber's mark and lubber line: a fixed line on a ship's compass indicating its heading

Other synonyms of lubber's mark include lubber's line, lubber's point.

lubber's mark (noun)	lubber line (noun)
a fixed line on a ship's compass indicating its heading	a fixed line on a ship's compass indicating its heading