'aquanaut' originates from Modern English, specifically formed from Latin 'aqua' where 'aqua' meant 'water' and Greek 'nautēs' where 'nautēs' meant 'sailor'.

'aquanaut' was coined in the mid-20th century as a blend modeled on 'astronaut', combining the prefix 'aqua-' and the element from Greek 'nautēs' to produce the modern English word 'aquanaut'.

Initially it referred specifically to persons who lived and worked in experimental underwater habitats; over time the term's core meaning has largely remained, though it is sometimes used more broadly for underwater explorers or long-duration divers.