Officers believe Tongee Bennett, 36, lost control of her SUV after coming off the bridge just south of Clayton off Barber Mill Road.
The SUV, carrying Bennett and her 13-month-old daughter, Rhiannon, went down an embankment and landed upside down in the water.
Terri Bogdanowicz saw smoke and hazard lights coming from Swift Creek as she headed to work.
"It was scary," Bogdanowicz said. "She called for help and said there was a baby, her and the baby, and that the baby was getting wet and we needed to go ahead and get her out."
About the same time, Mack Keen, a lineman with the town of Clayton, stopped to help.
Bennett was able to get her daughter out of the water, but she remained tangled in her seat belt.Water was up to her neck and Keen knew he had to work quickly.
"I didn't know if the car was going to finish falling in. I just wanted to hurry and get them out," he said.
Bennett and her daughter are doing well at WakeMed, where they are expected to be released later in the day.
Officials said Bennett will be charged with exceeding a safe speed.
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