Three members of the Karekare Surf Life Saving Club's emergency call-out squad attended within eight minutes of being notified, a statement said.
"Surf Lifeguards carried out CPR on the patient for 10 minutes until the Auckland Rescue Helicopter arrived and took the patient to hospital."
She died shortly after arriving at Starship Hospital.
A Surf Life Saving New Zealand spokesperson said their thoughts were with the family and friends of De Luen.
Her death will be referred to the Coroner and Surf Life Saving New Zealand's Coastal Safety team will also work with emergency services to establish the circumstances.
Friends and family of the teen are remembering her in heartfelt messages online.
'Thank you for being a great friend'
A family friend told the Herald the 14-year-old was very much loved and that she and her twin sister were well-known by whānau and friends as being "beautiful, caring girls".
"Also very loved by their uncles and aunties. Our children and their children and their mokos all grew up knowing each other and were referred to as cousins.
"Rest in love our angel. Fly high."
A parent of one of Portia's friends said he and his son were in a state of shock and could not believe the news.
"You will be forever in our thoughts and we will never forget the amazing person you are, were and always will be," he wrote on Facebook.
"Thank you from the bottom of our hearts for being such a great friend to my son," he wrote. "Rest in peace Portia."
TONE6, a single group of young vocalists, posted a tribute to the teenager on Facebook.
The six-strong sang The Winan's Gonna Be Alright, in the hope that it would bring some comfort to those grieving her.
:: Meet Portia De Luen from Glen Eden Primary School, the first prize winner of our Christmas Cup & Napkin Artwork...
Posted by The Coffee Club NZ on Thursday, 10 November 2016
A few years ago, the then-Glen Eden Primary School student won her school $4000 in a Christmas art competition run by The Coffee Club NZ.
Her drawing - depicting a cow and a sheep helping a kiwi bird put a star on top of a Christmas tree - came out on top of more than 300 entries from over 30 schools around the country.
As the winning entry, her design appeared on large-sized takeaway coffee cups in 60 cafes around New Zealand.
Family and friends are now rallying around Portia's parents and siblings - a twin sister and a brother.
Her father's employer has also launched a fundraising effort on Givealittle in a bid to help raise funds for the young family.
The company, UMS NZ Ltd, wrote: "This fundraiser will help raise money to provide financial help to [his] family during this tremendously difficult and heartbreaking time."
