A 16-year-old boy drowned at Lake Pegasus in Canterbury just after midday today.
Police said the boy had been swimming in the lake with a group, but got into trouble. The others tried to assist him but he slipped away.
His body was found 20 minutes later.
Local iwi have placed a rahui (ritual prohibition) on the lake and people have been asked not to swim there until it has been blessed and the tapu has been lifted.
Connor Roberts, a spokesman for the Todd Property Group, which owns the Pegasus Town development, said the company expressed its condolences.
"This is an extremely distressing time for the family and we express our condolences to all those involved. Given the the lead up to Christmas, this is extra tragic."
Police and ambulance attended the scene.
The boy's family had been notified, and the death will be referred to the coroner.
- Fairfax Media