frogman vs scuba diver

frogman and scuba diver both are nouns.

Word	Noun	Adjective	Verb	Adverb
frogman	Yes	No	No	No
scuba diver	Yes	No	No	No

As nouns, scuba diver is a hyponym of frogman; that is, scuba diver is a word with a more specific, narrower meaning than frogman:

Other hyponyms of frogman include deep-sea diver, pearl diver, pearler.

frogman (noun)	scuba diver (noun)
someone who works underwater	an underwater diver who uses scuba gear