submerse vs plunge

submerse is not a noun while plunge is a noun.

Word	Noun	Adjective	Verb	Adverb
submerse	No	No	Yes	No
plunge	Yes	No	Yes	No

As verbs, plunge is a hypernym of submerse; that is, plunge is a word with a broader meaning than submerse:

Other hypernyms of submerse include immerse.

submerse (noun)	plunge (noun)
	a brief swim in water
	a steep and rapid fall

submerse (verb)	plunge (verb)
put under water	begin with vigor
sink below the surface; go under or as if under water	devote (oneself) fully to
	cause to be immersed
	immerse briefly into a liquid so as to wet, coat, or saturate
	thrust or throw into
	fall abruptly
	drop steeply
	dash violently or with great speed or impetuosity