watermark vs marker

watermark and marker both are nouns.

Word	Noun	Adjective	Verb	Adverb
watermark	Yes	No	No	No
marker	Yes	No	No	No

As nouns, marker is a hypernym of watermark; that is, marker is a word with a broader meaning than watermark:

watermark: a distinguishing mark impressed on paper during manufacture; visible when paper is held up to the light
marker: a distinguishing symbol

Other hypernyms of watermark include mark, marking.

watermark (noun)	marker (noun)
a distinguishing mark impressed on paper during manufacture; visible when paper is held up to the light	some conspicuous object used to distinguish or mark something
a line marking the level reached by a body of water	a writing implement for making a mark
	a distinguishing symbol