In Greek mythology, Thetis (Greek: Θέτις) is a sea nymph. She is one of the fifty Nereids, the daughters of Nereus and Doris. Like other sea figures, Thetis bore the gift of prophecy as well as the ability to change her shape at will. She was married to the mortal hero Peleus. Their son is Achilles.
Media related to Thetis at Wikimedia Commons