biological science vs underwater

biological science is a noun but underwater is not a noun.

Word	Noun	Adjective	Verb	Adverb
biological science	Yes	No	No	No
underwater	No	Yes	No	No

biological science (noun)	underwater (noun)
the science that studies living organisms

biological science (adjective)	underwater (adjective)
	growing or remaining under water
	beneath the surface of the water