The death is one of three in or around water over the weekend, two of which occurred in Lower Hutt.
The incident was reported shortly after 8pm on Saturday at Motutawa Avalon Park, a police statement said.
"A child was retrieved, unresponsive, from a body of water. CPR was undertaken but sadly, the child could not be resuscitated."
The death would be referred to the coroner, police said.
The second Lower Hutt death occurred at Eastbourne this morning.
Emergency services responded to a report of a person requiring medical assistance on Eastbourne Beach around 10.40am.
Police said CPR was immediately provided upon arrival but the person was unable to be revived.
The circumstances of the incident are still unclear; however, the death will be referred to the Coroner.
The third death occurred off the coast of Moutohora Island in Whakatāne last night.
A man was recovered from the water unresponsive after jumping off the side of a boat around 9pm.
CPR was commenced but efforts to resuscitate him were unsuccessful.
The death is not being treated as suspicious and will be referred to the Coroner.
Meanwhile, a search is continuing for a man who had jumped off Pukete Bridge into the Waikato River in Hamilton yesterday evening.
Police and Fire and Emergency undertook an extensive search of the water and riverbank but did not find him.
The search resumed this morning.
