The coronial inquiry into the deaths of four people at Dreamworld gets underway this week.

The coronial inquest is investigating the deaths of Kate Goodchild, her brother Luke Dorsett, his partner Roozi Araghi and Cindy Low, who all perished on the Thunder River Rapids ride at Dreamworld in October 2016.

The raft the four were riding collided with a stranded vessel after a large water pump feeding the ride failed.

One the first day of the hearings, the inquiry was told that not one single event caused the incident, but rather a series of operator procedures and design faults.

The inquest also heard a memo had been sent to Dreamworld staff in the days before the incident that discouraged operators from pressing an emergency stop button.

Using the button could have shut down the ride almost instantly.

On the day of the tragedy, the ride broke down several times, leading operators to rely on a simple “scumline” rather than a ruler or device to gauge whether the water level was adequate.

The Australian Workers Union (AWU) says the inquiry could help address the behaviours of Dreamworld management.

AWU acting branch secretary Steve Baker said the union had been concerned about Dreamworld's approach to safety matters for some time.

“The AWU has taken a proactive role in pursuing these concerns about safety with Dreamworld management,” Mr Baker said.

“A major concern has been a culture of secrecy in the behaviour of Dreamworld.

“Whenever the union sought documentation from Dreamworld regarding safety issues, these requests were refused.

“This meant the union had to pursue this information through other means including Right to Information processes.”

The hearings continue.