aquanaut vs skin-diver

aquanaut and skin-diver both are nouns.

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

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

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

aquanaut (noun)	skin-diver (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