A firefighter who helped rescue a woman after her car flipped into an icy river says she may have been saved by a heart-shaped box of Valentine chocolates.

The woman spent nearly two hours trapped in the freezing water early on Valentine's Day after her SUV slipped off the road and fell into the Kootenay River.

Her boyfriend went looking for her when she didn't turn up for work and found a faint set of tire tracks leading to the river.

"The first stroke of luck was that he even found the tire tracks in the snow," Simon Grypma, assistant chief of Nelson Fire and Rescue, told the Nelson Daily News. "They were so faint, you could barely see them."

The boyfriend called for help after he found the SUV nine metres down a bank, resting upside-down in about 1.5 metres of water.

"We had to break through the ice to get to the vehicle," Beasley fire Chief Al Craft told the News. "We tried all the doors, popped the window, we couldn't open anything."

Craft wasn't able even to see the woman until a tow truck pulled the vehicle over on its side.

"She was stuck between the two seats, with her head in front of the back seat," he said. "She was breathing out of an air space near the footwell."

Grypma said the woman found a plastic container of chocolates – a Valentine's Day gift from her family – floating in the car.

He said the chocolates probably helped to keep her alive by providing a small amount of extra body heat. "She started to eat them, which I think helped."

The firefighters finally managed to rescue the woman through a window. She was taken to hospital, treated for hypothermia, and released later in the day.

"This woman's courage was incredible," Grypna said. "For her to hold herself together, with her thoughts and her actions, to save herself. She said she was praying to God her boyfriend would come and find her."