A senior ride operator at Dreamworld pushed a stop button "two or three times" before two rafts collided on the Thunder River Rapids ride, killing four people, a court has heard.
Peter Nemeth has taken the stand today as part of a coronial inquest into the deaths of Kate Goodchild, Luke Dorsett, Roozi Araghi and New Zealander Cindy Low at the Gold Coast theme park in October 2016.
Mr Nemeth said he was told by a supervisor before he started his shift on the ride that the pump had failed twice.
The inquest has previously heard that one of two large water pumps feeding the ride failed, causing water levels to drop significantly and leaving one raft stranded on a conveyor belt.
He said the conversation was along the lines of: "The pump has gone down twice and if it happens once more we would have to stop operating the ride for the day."
He said he noticed the water levels had dropped once he had begun operating the ride.
"By the time you noticed anything wrong the water level had dropped substantially?" Ken Fleming QC asked.
"Yes," he replied.
Mr Nemeth was asked about the collision between two the rafts, which resulted in the deaths of four people.
"I saw the second raft coming over the top of the conveyor … so about five to 10 metres between them," Mr Nemeth said.
"What button did you press?" Mr Fleming asked.
"The one to stop the conveyor moving," he replied.
"How many times did you press that button?" Mr Fleming asked.
"I turned around and I pressed it more than once to make sure the raft stopped before it collided with the other one," Mr Nemeth said.
"Did the conveyor stop?" Mr Fleming asked.
"No, it did not stop, even though I had pressed it, as I said, two or three times," Mr Nemeth told the court.
"It did eventually stop but that was when the rafts collided."
Investigators say the button was pressed too late.
Earlier the court heard a "slow stop" button on the main control panel of the Thunder River Rapids ride was "probably" pressed about 10 seconds after the four people were thrown from the raft.
Forensic crash investigator Senior Constable Steven Cornish told the court he reviewed the CCTV about "1000 times" and said the button was likely pressed after some of the victims were already in the water.
"Assuming it was pressed, it looks like it wasn't pressed until the raft was inverted," he said.
The forensic crash investigator told the inquest all the operational components of the ride were working as normal on the day of the fatal incident.
"When you checked the operation of the various components of the ride, you didn't find anything important did you?" Bruce Hodgkinson SC, barrister for Ardent Leisure, asked.
"I didn't find them to be faulty no," he replied.
The court heard the Thunder River Rapids ride relied on "operators to be in control".
"There's no automated safety," Senior Constable Cornish said.
"It's relying on human intervention."