The man, in his 60s, was taken to Dunstan Hospital in a serious condition.
The ute he was driving has since been removed from Lake Dunstan and an investigation into the cause of the crash is under way.
Meanwhile, a motorcyclist has died following a collision between a motorbike and a car near Eyrewell Forest in rural Canterbury.
The incident occurred shortly after 8pm and one person travelling in the car suffered critical injuries a police spokesperson said.
The incident occurred at the intersection of Poyntzs Rd and South Eyre Rd.
The intersection remains closed and is expected to stay closed until early this morning. Motorists are asked to avoid the area.
The serious crash unit is investigating the circumstances surrounding the crash.
Elsewhere one patient was being flown to Christchurch Hospital in a serious condition after a motorcyclist crashed into a bank near Hurunui.
The incident occurred on Dommett Rd, part of State Highway 1 in Canterbury.
Seven people have died on the country's roads in the last two days, bringing the road toll to 247 for the year to date.
Annual road deaths in New Zealand increased from 253 in 2013 to 380 last year.
The number of serious injuries jumped from 2788 to 3264 per year over the same period.