SELEMNOS was a River-God of Akhaia in the Peloponnesos, southern Greece. He was once a mortal boy, who loved the sea-Nymphe Argyra. When the Nymphe abandoned him, Aphrodite transformed the weeping youth into a river.
His river flowed north from Mount Panakhaikos, emptying into the Korinthian Gulf near the town of Argyra. The most important neighbouring rivers were the Elisson in the east, and Erymanthos to the south.
Pausanias, Description of Greece 7. 23. 1 (trans. Jones) (Greek travelogue C2nd A.D.) :
"After the Kharadros [in Akhaia] you come to some ruins, not at all remarkable, of the city Argyra, to the spring Argyra, on the right of the high road, and to the river Selemnos going down to the sea. The local legend about Selemnos is that he was a handsome lad who used to feed his flocks here. Argyra, they say, was a Sea-Nymphe, who fell in love with Selemnos and used to come up out of the sea to visit him, sleeping by his side.
After no long while Selemnos no longer seemed so handsome, and the Nymphe would not visit him. So Selemnos, deserted by Argyra, died of love, and Aphrodite turned him into a River. This is what the people of Patrai say. As Selemnos continued to love Argyra even when he was turned into water, just as Alpheios in the legend continued to love Arethousa, Aphrodite bestowed on him a further gift, by blotting out the memory of Argyra.
I heard too another tale about the water, how that it is a useful remedy for both men and women when in love; if they wash in the river they forget their passion. If there is any truth in the story the water of the Selemnos is of more value to mankind than great wealth."
- Pausanias, Description of Greece - Greek Travelogue C2nd A.D.