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A Mermanaut is an explorer of the aquatic realm. This exploration may take the form of spiritual, physical, or mental exploration of the planets vast oceans, and the worlds, secrets, and treasures they contain.

The word is a compound of mere, mermaid/man, and naut.

Mere is the Old English word for sea. With the addition of “ma” (merma) both genders of mermaid and merman are represented. Finally, the term "naut" is from nautes (greek: ναύτης), meaning sailor.
Q: So...How come you are so into diving?

(ALSO: sailing, boating, kayaking...etc.)

A: Because I am a Mermanaut.
by P053!D0|\| March 30, 2011