North Shore Police constables Paul Watts and Simon Russell say they were just doing their job after rescuing a woman from a sinking car in Auckland's Waitemata Harbour.

Two police officers who saved a woman who was seconds from drowning in her car that went into the water in Auckland's Waitemata Harbour say it's just another day on the job.

Constable Paul Watts said the rescue was "pretty much part of a routine job being a police officer", someone just happened to have a camera to capture this event.

Watts said the rescue took about 40 seconds.

Stuff.co.nz Rescuers plunged into the water to save a woman, whose car went into the water at Northcote Point in Auckland.

The car was fully-submerged within a minute after the officers dragged the woman to safety.

Watts and fellow rescuer Constable Simon Russell received calls from Police Commissioner Mike Bush this afternoon, commending them on their efforts.

Russell, who was at home painting when he received the call, said 'it's just another day on the job sir'.

While the pair remained humble about the gutsy rescue, North Shore Area Commander Inspector Shanan Gray said police was "very proud" of their efforts.

"The outcomes speak for themselves."

Gray said the men, with the help of the public, saved a woman who was seconds from drowning.

Police was appreciative of the actions of the public, he said.

The woman was in a stable condition in North Shore Hospital and police was investigating how the car got into the water.

Russell also sustained a minor injury to his left hand while rummaging on the seabed for something to use to smash the car window so he could get to the woman. He eventually found a spanner under the water.

In the meantime, North Shore Times reporter Simon Maude handed Watts a large rock, which he used to smash the rear windscreen.

Russell said it was good to have a plan B.

'LUCKY TO BE ALIVE'

The officers hauled the 63-year-old woman out onto dry land and waited for an ambulance crew to arrive.

She is expected to make a full recovery, police said this evening.

Detective Sergeant Callum McNeill said police were still trying to work out what happened.

The woman was in shock and has a "few cuts and bruises and is lucky to be alive," McNeill says.

Erwin Kampos was fishing nearby when the drama unfolded.

"I saw the BMW go in, either trying to turn or....it just went straight in," he said.

"I went into the water and tried to smash the window. The two police officers smashed the back windscreen, I tried to smash the sides and they didn't want to break. We were running out of time because the vehicle was filling up," he said.

"The police officers smashed the back window and dragged the lady out."

The car sank to the bottom of the harbour.

Leigh Keown, who worked at the nearby function centre The Wharf, said she heard noises and shouting.

She went outside to see the car sinking with the woman inside.

"The car was filling up fast. They got to her just in the nick of time."

A man on scene had raised the alarm, she said.

"And thank goodness he did."

THE INCREDIBLE RESCUE (Photos: SIMON MAUDE/Fairfax NZ)

An officer wades into the water to reach the car.

Another officer gets into the water while his colleague tries to break a window in the car.

An officer prepares to smash the window.

The woman climbs to safety.

Officers help her escape the car.

The car continues to sink as police pull the woman out.

The woman is carried to shore.

The car sits below the water.