aquanaut vs swimmer

aquanaut and swimmer both are nouns.

Word	Noun	Adjective	Verb	Adverb
aquanaut	Yes	No	No	No
swimmer	Yes	No	No	No

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

aquanaut: 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 aquanaut include bather, natator.

aquanaut (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 skilled worker who can live in underwater installations and participate in scientific research	a person who travels through the water by swimming