What we know about the Thunder Rapids Ride

DREAMWORLD'S THUNDER RIVER RAPIDS RIDE:

* Riders board six-person circular rafts which follow initial path through a cave before experiencing the rapids section of the ride

* Takes four minutes in total and hits top speed of 45km/h

* Riders are usually splashed with water as rafts spin through the rapids and hit walls

* Conveyor belt takes rafts back to start of the ride for passengers to hop in and out

* It's understood a raft flipped over on the conveyor belt after a malfunction, killing four passengers - two men and two women

* Ride located in the Gold Rush section of Gold Coast's biggest theme park and considered one of Dreamworld's most "family friendly"

* Opened in 1986 and remains one of park's oldest rides