skin-diver vs aquanaut

skin-diver and aquanaut both are nouns.

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

As nouns, skin-diver and aquanaut are synonyms defined as:

skin-diver and aquanaut: an underwater swimmer equipped with a face mask and foot fins and either a snorkel or an air cylinder

skin-diver (noun)	aquanaut (noun)
an underwater swimmer equipped with a face mask and foot fins and either a snorkel or an air cylinder	an underwater swimmer equipped with a face mask and foot fins and either a snorkel or an air cylinder
	a skilled worker who can live in underwater installations and participate in scientific research