go under vs submerge

go under and submerge both are verbs.

Word	Noun	Adjective	Verb	Adverb
go under	No	No	Yes	No
submerge	No	No	Yes	No

As verbs, submerge is a hyponym of go under; that is, submerge is a word with a more specific, narrower meaning than go under:

Other hyponyms of go under include settle, subside, founder, submerse.

go under (verb)	submerge (verb)
be called; go by a certain name	fill or cover completely, usually with water
go under	cover completely or make imperceptible
disappear beyond the horizon	put under water
	sink below the surface; go under or as if under water