Two mates who had been drinking at a Christmas function in Christchurch crashed on the same road about 30 seconds apart on Thursday night.
One of the vehicles flipped and landed upside down in a water race on Lincoln Tai Tapu Rd, Rolleston, about 10pm. The other vehicle also ran off the road and landed in a dry ditch.
Senior Constable Andy Williamson said the upside-down was lucky to survive: "I don't know how the hell he got out. He was lucky he wasn't killed."
Both drivers were out of their vehicles when emergency services arrived.
When police tested them for alcohol, one recorded more than 900mcg of alcohol per litre of breath - and the other more than 500mcg, Williamson said. Both drivers are under the age of 20.
The legal limit for those under-20 is zero and 250mcg for those over 20. The drivers were heading to Tai Tapu when they crashed.
"It is just stupidity," Williamson said.
"They knew they would have to get home at some stage and drove anyway."
Lincoln deputy fire officer Roger McClenaghan said the car that landed upside down was "an absolute mess".
"I'm not sure if the second guy was looking at his mate that had just crashed and then crashed himself," he said.
Both will be charged with driving with excess breath alcohol and will appear in the district court.
The crashes followed a busy weekend of crashes for the Lincoln fire crew.
On Saturday, firefighters cut two women from a vehicle after it rolled on the Christchurch Akaroa Rd, near Tai Tapu, about 4.45pm. They were taken to Christchurch Hospital.
On Sunday, a 45-year-old man was cut from his vehicle after a crash on Edward St, Lincoln. He was taken to hospital.