He was also unable to maintain a hold on the boy due to the heavy surf.
He was joined by a few members of the public who tried to help.
A second officer entered the water and reached the boy. He tried to bring the boy back to shore but had to battle to maintain a grip on him in the heavy surf. At times he lost hold of the boy, who was underwater for up to 20 seconds at a time and fading fast.
Police instructed members of the public and other police staff to form a human chain and this, combined with the second officer moving the boy towards the shore, saved him.
When the boy was brought to shore he was unresponsive, physically spent, and could not move unaided, police said.
He was given first aid on the beach by members of the public.
The first two officers, who by this stage were also exhausted by the surf, were also assisted to shore.
The conditions at the time were treacherous with dumping waves and an extremely strong undertow.
The boy was taken to Hawkes Bay Hospital but had since being discharged.
Police said they were proud of the heroism displayed by their officers and the members of the public.