Emergency services were notified about 3.30pm after a passing boat located several people in the water.
Police and Westpac Rescue helicopters responded and a total of four people were recovered from the water with the assistance of the crew in the boat.
The two people still alive were landed at Whatipu Beach where they were treated by Westpac Rescue Paramedics before being flown to hospital for further checks.
It is believed that the victims were in a five-metre boat that was launched from Onehunga and was swamped while crossing the Bar.
They are understood to have been in the water for about two hours before they were spotted by the passing boat, police said.
No details of the people involved were available and their identities would not be released until next of kin had been informed.
Police would investigate the deaths on behalf of the coroner.
- NZME.
