Glaucus. In Greek mythology, Glaucus was a Greek prophetic sea-god, born mortal and turned immortal upon eating a magical herb.
It was believed that he came to the rescue of sailors and fishermen in storms, having earlier earned a living from the sea himself. Glaucus's parentage is different in the different traditions, Nereus; Copeus; Polybus, son of Hermes, by Euboea, daughter of Larymnus; Anthedon and Alcyone; and lastly Poseidon and the nymph Nais.
The story of Glaucus's deification was dealt with in detail by Ovid in Metamorphoses and briefly referenced by many other authors. According to Ovid, Glaucus began his life as a mortal fisherman living in the Boeotian city of Anthedon.
He found a magical herb which could bring the fish he caught back to life, and decided to try eating it. The herb made him immortal, but also caused him to grow fins instead of arms and a fish's tail instead of legs, forcing him to dwell forever in the sea. Glaucus was initially upset by this side-effect, but Oceanus and Tethys received him well and he was quickly accepted among the deities of the sea, learning from them the art of prophecy.
John Tzetzes adds to the above story that Glaucus became immortal, but not immune to aging. In an alternate, non-extant version cited in Athenaeus, Glaucus chased a hare on Mount Oreia until the animal fell down almost dead, then carried his prey to a spring and rubbed