A term used to describe an individual who explores the depths of the ocean, in similarity to an astronaut who explores the depth of outer space, experiencing almost similar external environmental factors as an astronaut.
When Neil Armstrong did a big leap for mankind as an astronaut on the moon, Sylvia Earle leapt a great deal as an aquanaut in the oceans.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.