Sealab inhabitant

• Undersea explorer
• Bathysphere user
• Skilled underwater worker or scientist — an ace out (anag)
• Sub tenant?
• Sealab dweller
• Cousteau, for instance
• Underwater explorer
• A skilled worker who can live in underwater installations and participate in scientific research

Wiktionary Word definitions in Wiktionary
n. 1 An explorer in a submarine. 2 Someone who lives or works underwater, for scientific reasons.