immersion vs sinking

immersion and sinking both are nouns.

Word	Noun	Adjective	Verb	Adverb
immersion	Yes	No	No	No
sinking	Yes	No	No	No

As nouns, sinking is a hypernym of immersion; that is, sinking is a word with a broader meaning than immersion:

immersion (noun)	sinking (noun)
a form of baptism in which part or all of a person's body is submerged	a descent as through liquid (especially through water)
the act of wetting something by submerging it	a slow fall or decline (as for lack of strength)
complete attention; intense mental effort	a feeling caused by uneasiness or apprehension
sinking until covered completely with water
(astronomy) the disappearance of a celestial body prior to an eclipse