A river god, the son of Oceanus and Tethys. Alpheus fell in love with Arethusa, a follower of Artemis (also listed as a Nereid in some accounts). Frightened, Arethusa fled from Alpheus, but was unable to outrun him. She called out to Artemis to help her, and the goddess turned her into a spring, opening a tunnel under the sea from Greece to Sicily. As Arethusa became a spring, Alpheus became a river again, mingling his waters with those of Arethusa.
E2 Dictionary of Classical Mythology