One of the two operators managing the Thunder River Rapids ride at Dreamworld on the day four people were killed had only been trained that morning, a court has heard.

Senior ride operator Peter Nemeth told the inquest his younger colleague Courtney Williams, who was managing the ride with him, only started that day.

"Was that her first day?" counsel assisting the inquiry Ken Fleming QC asked.

"Yes, I found out she was trained that morning," Mr Nemeth replied.

Mr Fleming suggested training documentation obtained from Dreamworld looked as though Mr Nemeth had only been trained as high as a level two operator — but Mr Nemeth said he recalled being trained up to a level three.

Mr Nemeth has taken the stand as part of a coronial inquest into the deaths of Kate Goodchild, Luke Dorsett, Roozi Araghi and Cindy Low at the Gold Coast theme park in October 2016.

Operator 'surprised' there was an emergency stop

Mr Nemeth said he was "surprised" to learn there was an emergency stop button near the level two operator that could halt the conveyor within two seconds.

He testified he would have been able to shut the ride down more quickly had he have known.

"But you didn't do that because you didn't know it was possible?" barrister Matthew Hickey, acting for Ms Low's family, asked.

"Yes, that's correct," Mr Nemeth replied.

Earlier on Tuesday, Mr Nemeth told the court he pushed a "slow stop" button on the main control panel "two or three times" before two rafts collided, killing the group.

The button could stop the conveyor in eight seconds.

On Monday, the court heard Ms Williams had access to the emergency button, but she told police she was not aware what the switch really did.

Roozi Araghi, Luke Dorsett, Kate Goodchild, and Cindy Low lost their lives on the ride. ( Facebook )

Mr Nemeth was asked about the collision between the two rafts, which resulted in the deaths of the 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."

The ride operator said water levels dropped before he noticed anything was wrong. ( AAP: Dan Peled )

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 with his supervisor 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.

Investigators says a "slow stop" button was pressed 10 seconds after four people were thrown from the raft. ( AAP: Dan Peled )

Investigators say button was pressed too late

Earlier the court heard the slow stop button 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."

Ride 'more stressful' than others to manage

Under cross-examination by Mr Hickey, Mr Nemeth told the inquest he was never made aware of previous incidents in which rafts had collided on the Thunder River Rapids ride.

Previous incidents January 2001 — Collision of rafts due to operator error

January 2001 — Collision of rafts due to operator error October 2004 — A visitor fell into the water while unloading when rafts bumped together

October 2004 — A visitor fell into the water while unloading when rafts bumped together August 2005 — Three rafts mounted up together at the same time

August 2005 — Three rafts mounted up together at the same time 19 October 2016 — Water pump failed but nobody hurt

19 October 2016 — Water pump failed but nobody hurt 25 October 2016 — Two water pumps failed at 11:50am and 1:09pm

25 October 2016 — Two water pumps failed at 11:50am and 1:09pm 25 October 2016 — Fatal incident at 2:00pm when pump failed and two rafts collided on conveyor

"It would have made me more considerate of what I would do to operate the ride," he said.

Mr Nemeth said as a level three operator he was never trained in the mechanics of the ride and knew only of "the basics" to manage it.

He told the court he was aware of "regular" breakdowns on a number of different rides at Dreamworld and could recall multiple shutdowns.

Mr Nemeth said the Thunder River Rapids ride was "more stressful" to operate than other rides because he was responsible for watching the water pumps, electrical issues, three different lines of visitors and also overseeing the level two operator.

He agreed with Mr Hickey that it would have made his job easier to have some of those responsibilities removed.