plunge vs submerse

plunge is a noun but submerse is not a noun.

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

As verbs, submerse is a hyponym of plunge; that is, submerse is a word with a more specific, narrower meaning than plunge:

Other hyponyms of plunge include dip, dunk, dip, douse, dunk, plunge, souse, dip, dip, submerge, soak, sheathe.

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

plunge (verb)	submerse (verb)
begin with vigor	put under water
devote (oneself) fully to	sink below the surface; go under or as if under water
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