A Dreamworld ride operator was unsure which emergency button to press to prevent the Thunder River Rapids ride tragedy, an inquest has heard.
The principal police investigator has told a packed Southport Coroners Court the main control panel for the ride was confusing and the operator had previously been deterred from using an immediate shut down button.
On the opening day of the inquest into the October 25, 2016 tragedy which killed four people, the court also heard of a history of malfunctions on the Thunder River Rapids.
Detective Sergeant Nicola Brown said the water pump on the supposed family-friendly ride at the Gold Coast theme park stopped working twice in the hours before the fatal incident.
Det Sgt Brown said no engineering staff attended the second time, and that it was simply reset.
Less than an hour later, the pump stopped working a third time, resulting in the water level near the unloading point of the ride to drop so rafts were no longer buoyant but were sitting on maintenance rails.