Eight people were involved in a jet boat crash on the Waimakariri River which resulted in six being injured.
Emergency services were called to the scene near Springfield just after 3pm yesterday.
A police spokesperson said three people were flown to hospital with serious injuries, and three other people sustained minor injuries.
The Canterbury Westpac Rescue Helicopter and the ROA Rescue Helicopter based in Greymouth transported the three seriously injured people to Christchurch Hospital, a Maritime New Zealand spokesperson said.
It is unclear how the crash occurred but it involved a recreational jet boat, not a commercial one, the spokesperson said.
They were alerted when a safety locator beacon was set off.
Maritime NZ is investigating the incident.
Motorists are being warned to expect hazardous driving conditions.