The child, who was submerged, was rescued by the heroic actions of her father.
Police Coastal Master Garry Larsen said it was a miracle the girl survived.
"We're very lucky we're not dealing with something more serious," he said.
After rescuing his daughter, the man carried her back to the safety of North Wharf.
But her hurt mother was unable to get back on to the dock because of her injuries.
She was ultimately rescued by crew on a police boat, and, with her daughter and husband, was ferried back to the Police Maritime base at Mechanics Bay before being taken to Auckland City Hospital.
Larsen said it appeared the family was on a walk when the near-tragedy occurred.
"The child slipped and fell into the water and her parents went into the water after her," said Larsen.
"It was a lucky escape," he said. "They were just walking around and things happened very quickly."
It is understood the family were tourists from Europe.
Alpa Bandari was having dinner at a nearby restaurant when she heard a woman scream, "my baby, my baby".
"Everyone started gathering around and a woman jumped in the water to try to save the little girl," she said.
"Then there was another guy sitting at one of the tables who ran over and dived straight in and got the little girl out."
Bandari didn't realise the man was the girl's father. "It was really brave," she said. "I wanted to cheer but I didn't want to be the odd one out."
The family declined to comment on their ordeal last night.
