skin-dive vs swimming

skin-dive and swimming both are nouns.

Word	Noun	Adjective	Verb	Adverb
skin-dive	Yes	No	Yes	No
swimming	Yes	Yes	No	No

As nouns, swimming is a hypernym of skin-dive; that is, swimming is a word with a broader meaning than skin-dive:

skin-dive: underwater swimming without any more breathing equipment than a snorkel
swimming: the act of swimming

Other hypernyms of skin-dive include swim.

skin-dive (noun)	swimming (noun)
underwater swimming without any more breathing equipment than a snorkel	the act of swimming

skin-dive (adjective)	swimming (adjective)
	applied to a fish depicted horizontally
	filled or brimming with tears

skin-dive (verb)	swimming (verb)
swim underwater with no breathing apparatus other than a snorkel