Surf lifesavers and paramedics arrived at the scene within minutes and took over for half an hour, but were unable to resuscitate him. Police said the 7-year-old was "safe and well".
Northland Emergency Services Trust rescue helicopter chief pilot Pete Turnbull said they arrived at the scene minutes after they were alerted, as they were diverted from the search for an aircraft that turned out to fine.
Mr Turnbull said the group was isolated on a bank near the Waipu River mouth, near Ruakaka Beach.
"The beach was sparsely populated -- it's a very long beach and there were just wee pockets of people every 200 to 400 metres, otherwise you were pretty much on your own. The tide was half out so it was just a big isolated beach."
A man who owned a home near the river mouth said the area could be difficult for people who weren't familiar with the swimming conditions.