Okeanos is the deity of water and aether. He rules the great ocean, and all the seas and rivers are subservient to him. He also is lord of the roiling aether, which has its own currents and storms.
Tethys mirrors her husband in many ways, but whereas he is the lord of the water, she is the lady of those who live in it and on it. Most worship him rather than her. Tethys is worshipped mainly by sailors, whalers and fishermen, but is also the patron goddess of wetnurses and dairymaids. The Blue Friars also revere her as Sophia, goddess of wisdom.
Okeanos and Tethys are old, remote gods.