skin-diver vs bather

skin-diver and bather both are nouns.

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

As nouns, bather is a hypernym of skin-diver; that is, bather 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
bather: a person who travels through the water by swimming

Other hypernyms of skin-diver include natator, swimmer.

skin-diver (noun)	bather (noun)
an underwater swimmer equipped with a face mask and foot fins and either a snorkel or an air cylinder	a person who travels through the water by swimming
	a person who takes a bath