swimming vs skin-dive

swimming and skin-dive both are nouns.

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

As nouns, skin-dive is a hyponym of swimming; that is, skin-dive is a word with a more specific, narrower meaning than swimming:

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

Other hyponyms of swimming include bathe, skinny-dip, dip, plunge, dive, diving, floating, natation, skin diving.

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

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

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