diver vs adventurer

diver and adventurer both are nouns.

Word	Noun	Adjective	Verb	Adverb
diver	Yes	No	No	No
adventurer	Yes	No	No	No

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

diver: someone who works underwater
adventurer: someone who travels into little known regions (especially for some scientific purpose)

Other hypernyms of diver include explorer.

diver (noun)	adventurer (noun)
large somewhat primitive fish-eating diving bird of the Northern Hemisphere having webbed feet placed far back; related to the grebes	a person who enjoys taking risks
someone who dives (into water)	someone who travels into little known regions (especially for some scientific purpose)
someone who works underwater