In Greek mythology, the Old Man of the Sea (Ancient Greek: ἅλιος γέρων, romanized: hálios gérōn; Greek: Γέροντας της Θάλασσας, romanized: Yérondas tis Thálassas) was a figure who could be identified as any of several water-gods, generally Nereus or Proteus, but also Triton, Pontus, Phorcys or Glaucus. He is the father of Thetis (the mother of Achilles).[1]