Psamathe was the Nereid goddess of sand beaches. Her name means "the Sand-Goddess" from psammos, sand and theia, goddess.
Psamathe was the wife of Proteus, the old seal-herder of Poseidon. She bore him a mortal son and a sea-nymph daughter.
The goddess was also seduced by the Aiginetan king Aiakos (Aeacus) who ambushed her on the beach. She tried to escape his grasp by transforming herself into a seal, but he refused to give up and she conceded to his desires, bearing him a son named Phokos (Phocus, "the Seal").
The boy was the favorite of his father, which the jealousy of his half-brothers Peleus and Telamon. The pair conspired to murder him and were exiled from the island. Psamathe was aggrieved and sent a giant wolf to harass the flocks of Peleus. However, through the advise of Thetis, his wife and the sister of Psamathe, he managed to assuage the goddess with sacrifices