Lake Dunstan above the Clyde Dam.
The woman's car left the road just north of the Clyde Dam and plunged about 80m down a steep bank, landing in water about 20m deep.
Emergency services were notified of the crash about 6.30pm.
The woman escaped the sinking car and was picked up by a boatie, police southern communications shift commander Peter Hegarty said.
Her car had yet to be found at 9.45pm tonight.
The woman was taken to Dunstan Hospital with moderate injuries, and police are investigating the crash.
