diver vs explorer

diver and explorer both are nouns.

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

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

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

Other hypernyms of diver include adventurer.

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