"I turned around and thought 'where's Paulette gone' and then saw her floundering in the water and diving under. Then I noticed the kiddie's hat just floating in the water, it was such an awful feeling. The mother came running and other people began to rush over," Ms Anderson said.
"That little girl hadn't made a sound as she went over, or splashed around or anything. She just went down like a stone, and it had happened in an instant."
A youth worker and keen sportswoman, Miss Lewis' key and cellphone were lost during the plunge but she refused an offer from the child's grateful father to give her his own phone as a replacement.
"It's a small price to pay for the life of a child," she told her aunt. "I'll sleep well tonight knowing that little girl is alive."
Miss Lewis had tried to grab the child as she toppled from the pontoon but couldn't reach her.
"Even though there were quite a few people about, no one else noticed her go into the water, it was so quick," Ms Anderson said. "It is just typical of Paulette to act so quickly without any thought for herself. She didn't hesitate for a second and I am so proud of her."
Had her niece not seen the toddler fall and acted so quickly, the search would have been for a small body that could have been swept away on the turning tide, Mr Anderson said.
Far North District Council communications manager Richard Edmondson said an inspection of the pontoon yesterday showed a rubber fender strip, about 300mm above the water, had peeled off, exposing the head of a coach screw. It would be repaired today.