Five people rescued from the roof of a submerged car in Canterbury's Waimakariri River

Five people, including four-year-old twin girls, sought refuge on the roof of a Toyota Surf after it became submerged in the Waimakariri River's fast-flowing, frigid waters - resulting in a dramatic after-dark callout for Canterbury's Rescue Helicopter crew.

David O'Connor was driving the car. He and his partner had gone to rescue a friend who had become stuck with his three children crossing the Waimakariri River. They were driving the kids to safety when disaster struck. 

"The truck cut out and unfortunately we got stuck," O'Connor told Newshub.

His friend made it to shore - but O'Connor was now in trouble, with the water rising over the bonnet of the four-wheel drive. 

"We all clambered on to the roof of this thing and tried to be as patient as we could," he said.

The just-above-freezing temperatures made the situation all the more urgent for rescuers. 

Paramedic Tatsu Kawasaki was lowered down on a winch from the helicopter. Crewman Wayne Ledgerwood guided pilot George McInnes as one-by-one the group was lifted across to the riverbank

"The group stayed very calm on the roof of the vehicle and worked well with our team which made things easier," Canterbury Rescue Helicopter paramedic Wayne Ledgerwood told Newshub.

The group were checked over by ambulance staff and were given the all clear. O'Connor says their safety was all thanks to their rescuers.

"We'd still probably be in a bad way if they hadn't landed you know, so hats off to them."

Fortunately, the Toyota Surf was the only casualty of this daring late-night rescue.