The woman’s husband freed himself from the car and survived, police said.
The family of four was returning home after watching a film at a theatre on Lattice Bridge Road on Tuesday night when the accident took place.
Police identified the man as Pandian, 48, a resident of Singaravelan Street in Chinna Neelankarai, who swam to the shore and cried out for help. Passersby informed police, fire and rescue services.
A police team led by the Adyar deputy commissioner S Kannan rushed to the spot and firemen used a crane to pull the car out of the pond.
“The woman and her daughters were found dead in the car,” a police officer said. “The vehicle was found 9ft deep in water .”
Police sent their bodies to Government Royapettah Hospital for autopsy.
Police identified the victims as P Vennila, 38, and her daughters P Ramya, 20, a second-year degree student in an arts and science college in the city, and P Pavithra, a Class 11 student at a private school.
“It appears that Pandian lost control of his car after an MTC bus suddenly overtook his vehicle,” the officer said. “He said his wife and daughters cried out when the bus almost hit them and, in shock, he swerved to the left, causing the car to plunge into the pond.”
He said Pandian, who recently started a travel company in the city after working for Nerolac Paints, noticed the car was running out of fuel. He took a U-turn near Palkalai Nagar in Thiruvanmiyur to head to a fuel station on the opposite side of the road.
“The accident took place as they were nearing the fuel station,” the officer said.
Pandian told police officers that he released his seat belt and escaped through a door. He thought his family members also escaped but, trapped in the car, they drowned.
The Adyar traffic police have registered a case under IPC Section 304 (a) (death caused due to negligence) against Pandian.
photo for representation only