Tethys in Greek mythology

In Greek mythology, Tethys (Greek Τηθύς), daughter of Uranus and Gaia, was a Titaness and sea goddess who was both sister and wife of Oceanus.

She was mother of the chief rivers of the world known to the Greeks, such as the Nile, the Alpheus, the Maeander, and about three thousand daughters called the Oceanids.

Considered as an embodiment of the waters of the world she may be seen as a counterpart of Thalassa, embodiment of the sea.

(adapted from Wikipedia)