UPDATE: The dog was rescued around 8.30pm on Saturday night according to a CFA spokeswoman.
The dog was originally reported to be as far as 20 metres down but the fire service controller for the CFA said crews on scene thought it could be closer to the surface.
Ballarat City CFA has sent a rescue crew to Barrys Reef to assist and the Ballan brigade is also on scene.
The dog’s condition was not yet known.
Sign up for our newsletter to stay up to date.