skin-diver vs swimmer

skin-diver and swimmer both are nouns.

Word	Noun	Adjective	Verb	Adverb
skin-diver	Yes	No	No	No
swimmer	Yes	No	No	No

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

skin-diver: an underwater swimmer equipped with a face mask and foot fins and either a snorkel or an air cylinder
swimmer: a person who travels through the water by swimming

Other hypernyms of skin-diver include bather, natator.

skin-diver (noun)	swimmer (noun)
an underwater swimmer equipped with a face mask and foot fins and either a snorkel or an air cylinder	a trained athlete who participates in swimming meets
	a person who travels through the water by swimming