Mother-daughter pair were still alive after car plunged into canal
But the impact left them with several fractured ribs and neck injuries and they later drowned.
Both mother and daughter were still alive when their car plunged into Alexandra Canal on Jan 24.
But the impact left Madam Yep Lay Choo, 51, and her only child, student Kimberly Poon Hui Yin, 22, with several fractured ribs and neck injuries.
Delivering his findings into their deaths yesterday, State Coroner Marvin Bay said Ms Poon's neck was more seriously hurt than her mother's and it could have affected her ability to move to the rear of the overturned car - towards air pockets when water started entering the vehicle.
Coroner Bay, who found their deaths to be a "truly tragic misadventure", added that Madam Yep, who worked in the logistics and transportation industry, could have stayed behind in the vehicle to help her daughter until they drowned in the 3m-deep water.
Madam Yep's husband, businessman Robin Poon Joo Kim, 50, had earlier driven her and their daughter to Great World City Shopping Centre before handing her the keys to the car.
He left in a taxi around 6pm for a work-related meeting.
Madam Yep and Ms Poon went to the nearby Valley Point Shopping Centre at River Valley Road where they had dinner. They shopped for groceries and went to the basement carpark at 8.57pm.
Closed-circuit television footage shows their silver Mercedes-Benz E250 leaving the basement at "an apparent fast speed".
Instead of turning right to the road, it shoots straight ahead, goes over a kerb into some bushes, then swerves to the left before hitting the canal railing. The car travels some 15m in about 3sec before falling into the canal when the railing gives way.
Coroner Bay said: "The event was likely precipitated by a moment of inattention or distraction on the part of Madam Yep as she left the carpark, having stepped on the accelerator instead of braking.
"This case does underscore the need for motorists navigating less familiar carparks to proceed at a cautious speed, which would allow sufficient reaction time to avoid humps, obstacles or other unexpected features of the carpark."
The event was likely precipitated by a moment of inattention or distraction on the part of Madam Yep as she left the carpark, having stepped on the accelerator instead of braking.
- State Coroner Marvin Bay