sapropel vs goop

sapropel and goop both are nouns.

Word	Noun	Adjective	Verb	Adverb
sapropel	Yes	No	No	No
goop	Yes	No	No	No

As nouns, goop is a hypernym of sapropel; that is, goop is a word with a broader meaning than sapropel:

sapropel: sludge (rich in organic matter) that accumulates at the bottom of lakes or oceans
goop: any thick, viscous matter

Other hypernyms of sapropel include goo, gook, guck, gunk, muck, ooze, slime, sludge.

sapropel (noun)	goop (noun)
sludge (rich in organic matter) that accumulates at the bottom of lakes or oceans	street names for gamma hydroxybutyrate
	any thick, viscous matter