TIASA was the Naiad Nymph of the stream Tiasa and its springs which probably supplied the town of Amyklai in Lakedaimonia with water. She was a daughter of the local river-god Eurotas.

Pausanias, Description of Greece 3. 18. 6 (trans. Jones) (Greek travelogue C2nd A.D.) :
"As you go down to Amyklai (Amyclae) from Sparta [in Lakonia] you come to a river called Tiasa. They hold that Tiasa was a daughter of Eurotas."

Sources:

• Pausanias, Guide to Greece - Greek Geography C2nd AD