Witness tells of dramatic rescue after car goes into water near Sumner, Christchurch

Six men had already reached the car when the woman's friend got in the water. Photo / File

The police dive squad are this morning set to arrive in Christchurch to resume the search for a person believed to be trapped inside a car which plunged into the sea last night.

A witness has told of the frantic attempts by by-standers to free two people trapped in a submerged car which went off Main Rd in Christchurch and into the sea.

Rescuers managed to save the driver of the car - a man - but the passenger, believed to be his wife, is missing, feared dead.

Deborah Roberts, who was driving behind the car, which was heading away from Sumner, said the other driver failed to turn left at a bend in the road and instead went "absolutely straight".

"Not veer, not turn slightly, just straight."

Her friend Lucy Lewis and Roberts' two children were in the car with her and saw what happened.

"I stopped off to the side and [my friend] flew out. I parked up safely, instructed my kids to stay put, took the keys and ran over. My friend had taken off her things and jumped into the water after the car."

Six men had already reached the car when the woman's friend got in the water, she said.

"They managed to get the driver out and started pulling him to shore. They all started getting swept away and the car sank so quick."

The rescuers managed to get the man who had been in the crashed car safely to shore, but the current dragged some of his rescuers out to sea behind Shagrock, the woman said.

"Some of the helpers had to climb on the rocks to get out of the tide."

She told the Herald when the man got to shore he started asking where his wife was and the people who'd helped him started diving back under the water to try to find the car.

"The emergency services and lifeguards arrived then and no one could find the car."

The woman said she helped pull the man out of the water and made sure he was okay. He didn't appear to be injured and paramedics at the scene assessed him, she said.

"We gave our statement to the police. And stayed for awhile. Then I had to go back to my children."

Another witness at the scene also said the car, with a two occupants - a man and a woman - inside, appeared to have taken the corner too quickly and came off the road.

"It was pretty intense."

The second witness told the Herald the section of the beach where the car entered the water had a notorious undercurrent.

A local resident told Newstalk ZB a full emergency response , including police and an ambulance, had been issued, a chopper was circling above and lifeboat was out on the water.

Inspector Hirone Waretini confirmed the driver of the car was saved and had been taken to hospital for treatment.

Police believed another person had been in the car, Waretini said, but searchers were unable to find the person or car last night.

Traffic was being diverted while the Serious Crash Unit finished examining the scene.

Police asked road users to avoid the area if possible.​