This story is told in full only by Ovid. There is nothing noteworthy in his treatment of it. The verse at the end is taken from the Alexandrian poet Moschus.
In Ortygia, an island which formed part of Syracuse, the greatest city of Sicily, there is a sacred spring called Arethusa. Once, however, Arethusa was not water or even a water nymph, but a fair young huntress and a follower of Artemis. Like her mistress she would have nothing to do with men; like her she loved hunting and the freedom of the forest.
One day, tired and hot from the chase, she came upon a crystal-clear river deeply shaded by silvery willows. No more delightful place for a bath could be imagined. Arethusa undressed and slipped into the cool delicious water. For a while she swam idly to and fro in utter peace; then she seemed to feel something stir in the depths beneath her. Frightened, she sprang to the bank—and as she did so she heard a voice: “Why such haste, fairest maiden?” Without looking back she fled away from the stream to the woods and ran with all the speed her fear gave her. She was hotly pursued and by one stronger if not swifter than she. The unknown called to her to stop. He told her he was the god of the river, Alpheus, and that he was following her only because he loved her. But she wanted none of him; she had but one thought, to escape. It was a long race, but the issue was never in doubt; he could keep on running longer than she. Worn out at last, Arethusa called to her goddess, and not in vain. Artemis changed her into a spring of water, and cleft the earth so that a tunnel was made under the sea from Greece to Sicily. Arethusa plunged down and emerged in Ortygia, where the place in which her spring bubbles up is holy ground, sacred to Artemis.
But it is said that even so she was not free of Alpheus. The story is that the god, changing back into a river, followed her through the tunnel and that now his water mingles with hers in the fountain. They say that often Greek flowers are seen coming up from the bottom, and that if a wooden cup is thrown into the Alpheus in Greece, it will reappear in Arethusa’s well in Sicily.
Alpheus makes his way far under the deep with his waters,
Travels to Arethusa with bridal gifts, fair leaves and flowers.
Teacher of strange ways is Love, that knavish boy, maker of mischief.
With his magical spell he taught a river to dive.