The driver was trapped inside and was deceased.
A Lake Moeraki area resident told the Greymouth Star the driver and his three companions - two South Westland locals and an Irish visitor - had just marked the end of the whitebait season, having spent the past 10 weeks whitebaiting at the mouth of the Moeraki (Blue) River, and had been celebrating the end of the season.
The car was travelling very fast when it approached the bridge and "literally flew across the whole Moeraki River".
Those helping in the aftermath heard from the surviving occupants that they "had never been in a vehicle travelling so fast".
One of the passengers suffered a broken arm or wrist and was airlifted to Grey Base Hospital by the NZCC West Coast Rescue Helicopter.
The other two were treated at the scene for lacerations and shock.
The resident said it was usually local people picking up the pieces from visiting drivers crashing in South Westland, but ironically this time it was locals who needed help.
"It's a little bit sobering really."
He paid tribute to the trained local residents who were first on the scene who helped late into the night, with emergency services from Haast and Fox Glacier.
"The thing we pay credit to is the medical emergency professionals who are resident here who were on the scene and gave first aid for the first 45
minutes ... everybody performed marvellously."
The car, with the driver inside, was removed from the river about 1.30am yesterday.
Acting senior sergeant Paul Watson of Greymouth said a serious crash investigator who was on the West Coast yesterday to train local staff, was at the crash scene today and had opened a serious crash investigation.
- Greymouth Star, Otago Daily Times