Caitlin Ruddy had been with a group of teenagers on the north pier at Cullercoats Bay on Saturday evening.
Northumbria Police said she was rescued from the side of the bay by a member of the public.
Caitlin died in hospital after suffering a cardiac arrest. Her mother, Sabrina Cook, said she had lost her "everything".
Mrs Cook has warned young people "not to take water for granted, because it is dangerous".
"I've lost my daughter through it," she said.
"She was stunning, she was my everything really, she was my friend."
Caitlin's friends and family have been paying their respects at Cullercoats Bay, writing messages in the sand and leaving flowers.
A RNLI lifeboat, a Coastguard search-and-rescue helicopter and police were called to the scene at about 20:00 GMT.
Caitlin was taken to Northumbria Specialist Emergency Care Hospital in Cramlington.
Another 15-year old girl, and a boy and girl both aged 14, were also taken to hospital as a precaution but were uninjured, police said.
Ch Insp Paul Knox issued a warning that "people can be taken unawares by the strength of the waves" when it is dark and cold.
"People should always be careful around water and if the sea is looking rough with waves pounding on to the pier, we would advise people to be particularly cautious and keep their distance," he said.
A Cullercoats resident who witnessed the rescue operation said the weather had been "absolutely freezing".
Newcastle University lecturer Clare Guilding said the beach was a popular place for teenagers to congregate.
"It was minus 2C, but once you get out on the front it was just bitterly, bitterly cold," she said.

That compares with just 300 people in the largest trust area, Belfast.
It is thought that the problem in the South Eastern Trust is down to staffing issues in that area.
The trust - which covers Newtownards, County Down and Lisburn, said it has been unable to fill two consultant cardiologist posts.
There is also the added problem of staff sickness and increase in the number of referrals.
The South Eastern Trust serves a population of approximately 345,000 people with a budget of almost Â£500m.
The figures also show that 364 people are waiting up to a year for their first urgent consultant-led appointment at the Ulster Hospital, while in every other trust the waiting list for this type of appointment is zero.
In a statement, South Eastern Trust said:  "We have recently lost two consultant cardiologists who both required to relocate.
"Despite strenuous efforts, we have, so far, been unable to fill these vital posts and, combined with the constant increase in the number of cardiology referrals, this has led to an unfortunate increase in waiting times for appointments.
"We are taking every possible measure to address this."
A 15-year-old girl has died despite being rescued after she was swept into the sea in North Tyneside.
[NEXT_CONCEPT]
Almost 1,000 people in the South Eastern Health Trust are waiting for an urgent appointment to see a cardiologist, according to a report.