Synonyms for Diver (same or very similar meaning)
WordNet sense 1 (someone who works underwater):
frogman, underwater diverWordNet sense 2 (someone who dives (into water)):
plungerWordNet sense 3 (large somewhat primitive fish-eating diving bird of the northern hemisphere having webbed feet placed far back; related to the grebes):
loonFrom the ODE community, based on WordNetadd/edit