Someone with a Pisces astrological sign.

(astronomy, astrology) The Fish, a Greco-Roman constellation of the zodiac named for its presumed resemblance to a pair of fish and supposed to be ruled by Neptune and to influence events occurring between February 20 and March 20 (tropical) or, less often, between March 15 and April 14 (sidereal).

(figuratively) The domain of fish; the sea.