A woman is in a critical condition and a man is in a moderate condition at Waikato Hospital after the car they were travelling in crashed into the Waikato River.
Police earlier reported the woman had died, but have since said the information was wrong and that the woman regained a pulse after an hour of CPR.
She is in the intensive care unit at Waikato Hospital.
The car and trailer plunged into the river about 12.25pm today at the intersection of Tirau Rd and Shakespeare St in Cambridge.
A police spokeswoman said the car appeared to have gone through the roundabout and over the edge near the low-level bridge. Two people were in the car.
Witnesses called 111 saying they had seen two people in the water.
Fire and Emergency and St John Ambulance also attended and the man was taken to Waikato Hospital.
The woman was given an hour of CPR at the scene, police said.
Andrew Mackintosh was passing about five minutes after the crash and saw emergency services performing CPR before carrying the people up the bank to three waiting ambulances.
It appeared the car "hit a kerb, gone almost airborne, gone over the barrier, down the bank and into the water", Mackintosh said.
He said a crowd of up to 100 people had stopped to watch, delaying traffic in Cambridge.
Diversions are in place at the intersections of State Highway 1 and Tirau Rd, Cook St and Shakespeare St, and Achilles Ave and Dominion Ave, while the Serious Crash Unit investigates.