A Dreamworld paramedic was trying to resuscitate one of the victims of the Thunder River Rapids ride tragedy when the sinking water levels revealed another victim, an inquest has heard.

Four visitors died when the 30-year-old ride malfunctioned on October 25, 2016, their raft colliding with another before flipping on its side.

An inquest into the deaths of Cindy Low, Kate Goodchild, her brother Luke Dorsett and his partner Roozi Araghi is being held at the Southport Coroners Court.

Paramedic John Clark told the inquest despite being aware of the gravity of the situation upon his arrival at the scene, he didn’t know how many people had been in the raft when he began assessing patients.

After hauling one person from the trench of the ride and attempting resuscitation, a fourth victim was revealed as water drained from the site.

Mr Clark said it was impossible for him to know how much time had passed from when he began work on the patient to the fourth victim being revealed.

“If I was to tell you a time I’d be completely guessing,” Mr Clark said on Wednesday.

Mr Clark, who no longer works for the park, is one of four ex-employees who have begun legal action against Dreamworld’s parent company Ardent Leisure for psychological injuries suffered in the tragedy’s aftermath.

The inquest was also shown a letter from a Dreamworld staff union representative to senior management advising the park to eliminate human error or simplify shutdown procedures on rides before the tragedy.

The letter was sent after a similar incident in November 2014 on the Thunder River Rapids ride where two rafts containing visitors collided.

No one was injured in that incident but ride operator Stephen Buss was sacked for breaching park safety protocols.

In the letter the park is warned “some staff believe that supervisors are out to get them” and this was affecting performance.

The letter concludes the reliance on staff to shut down rides in emergencies increased the likelihood of incidents and it was advisable to “eliminate human error”.

It suggested the park should have just one button for staff to hit in an emergency shutdown.

At the time of Mr Buss’s termination, staff needed to hit four buttons in a sequence to correctly shut down the ride.

Mr Buss told the inquest he didn’t have an issue with the four-button procedure but conceded a single button shut down would “eliminate a time problem”.

Mr Buss said he was “confused” when he saw television footage of the 2016 tragedy, as shutting down the conveyor in an emergency had been “drummed” into him during his training.

“I don’t know why (the ride) wasn’t stopped,” he said.

Mr Buss also said he never undertook a practical emergency drill during his eight years at Dreamworld.

– AAP