A Canadian woman had to be rescued from the roof of her submerged car after driving into an isolated marsh as she relied on GPS navigation, police said Wednesday.

The Ontario Provincial Police said the woman called 911 emergency services on her cellphone for help, after she became lost on her way to work east of Toronto late Tuesday.

"She advised she was standing on top of her car as it was submerged in a heavy marsh," police said in a statement. "She was following her GPS (Global Positioning System) directions and became lost."

The vehicle had become stuck in mud and quickly began filling up with water.

Rescuers searched the conservation area until finally she was spotted "in the middle of the marsh" by firefighters dressed in wet suits who waded into the waist deep water.