- a person who lives and works underwater
- a person who swims or dives underwater
WordReference Random House Learner's Dictionary of American English © 2017
- Oceanographya scuba diver who works for an extended period of time in and around a submerged dwelling.
- Oceanographyan undersea explorer, esp. one who skin-dives from or lives for an extended period of time in a submerged dwelling.
- Oceanography, Sporta skin-diver.
- aqua- + -naut, on the model of aeronaut, astronaut, etc. 1880–85