A helicopter and specialist swimming teams were rushed out in the middle of the night to rescue motorists trapped in floodwaters.
Police said despite warnings not to travel due to flooding in the Taieri area south of Dunedin, a group of intoxicated young people became stranded on State Highway 87 and had to call emergency services.
The man who called police was sitting on top of his vehicle, with others trapped inside.
"Rescuers were required to carry out a rescue which, had those involved followed Civil Defence advice, would not have been required," said Otago Coast Area Commander, Inspector Kelvin Lloyd.
"Initially rescuers were unable to reach the group in the atrocious conditions, so a rescue helicopter was required."
Water Rescue swimmers were tasked to assist due to the rapidly-rising flood waters.
IRB teams managed to reach the group, finding nine people aged in their twenties inside two vehicles.
"All nine individuals appeared to be intoxicated and they were all suffering from hypothermia," Lloyd said.
"A number of them were in such an advanced state to the point where they need to be carried out."
They were transferred to waiting ambulances before all rescuers had to evacuate the area immediately due to the rising water levels.
"Those rescued chose to ignore advice to stay off the roads and put themselves and the lives of several rescuers at risk," Lloyd said.
"Without the assistance of these rescuers, we have no doubt that lives would have been lost."
The inspector reminded all members of the public that venturing out in such conditions, contrary to emergency services warnings, puts the lives of both the rescued and rescuers at serious risk.
"Rescuers and emergency services are here to help and will respond to issues as soon as possible, however everyone's role becomes significantly more dangerous when advice is not followed."