Irish tourist Brendan Hickey, 34, couldn't swim and had drunk several wines when he lost his balance and fell near the Home Nightclub in Cockle Bay at 10.55pm on May 23, 2014.

His friends and girlfriend initially thought he was joking when he landed in the six-metre-deep water and was seen flailing about.

Two friends jumped in after him but he had disappeared within seconds.

On Thursday, Deputy State Coroner Teresa O'Sullivan slammed Vivid Darling Harbour's organisers for "significant systems failures" and "obvious deficiencies" in event planning, including a risk assessment plan that made no mention of the risk of people falling into the water.

"Unfortunately, the evidence before this inquest left a distinct impression of uncertainty as to the procedures to be followed, and by whom, in the event of an emergency of this nature," she said in her findings.

Festival event manager Michael Prescott, from the subcontracted event management company Concept Entertainment Group (CEG), ordered that the 11pm light and sound show proceed as rescuers searched for Mr Hickey.

One of the first police officers on the scene said the music was so loud he could barely hear what Mr Hickey's friend was screaming from the water.

"I could barely communicate with my fellow officers that were standing next to me [let] alone the people in the water," he said.

Mr Prescott told the inquest he didn't cancel the show because large crowds leaving the area would hinder the search efforts. However, he conceded that he didn't consult with anyone on the ground and had no knowledge of the event's "Show Stop Procedure".

Ms O'Sullivan said it would have been more appropriate to consult with police but it's unlikely Mr Prescott's decision affected Mr Hickey's chance of survival, such was his level of intoxication and inability to swim. An autopsy returned a blood alcohol reading of .256.

"In the absence of an immediate in-water rescue, there was little, if any, prospect of Mr Hickey being rescued," she said.

Ms O'Sullivan detailed several systems failures and communication breakdowns between CEG, the then Sydney Harbour Foreshore Authority, festival organiser Destination NSW and other agencies.

For example, the precinct risk assessment was performed by someone from CEG with no formal risk assessment qualifications.

It made no mention of people falling into the water or of lifebuoys, patrol vessels and other lifesaving resources.

Plans were not cross-checked between organisations or distributed to rangers on the ground.

Ms O'Sullivan welcomed several changes made for Vivid in 2015 and 2016 - including temporary fencing - and was satisfied Destination NSW had improved their procedures. However she said CEG, who still run the festival, had not fixed its "underlying weaknesses" in risk assessment.

Among several recommendations, she said Sydney Harbour Foreshore Authority (now Property NSW) should erect temporary fences during large events and should undertake a review to see if permanent fencing would outweigh the design aims and public enjoyment of Darling Harbour.

The Minister for Finance, Services and Property Dominic Perrottet said the State government would "urgently consider" the recommendations.

A spokesman for Property NSW said "the use of permanent barriers will be considered as part of the ongoing strategic risk review".

CEG did not respond to calls and emails.

Shane Hickey told the inquest the death of his brother, who had been travelling around Australia with his girlfriend in 2014, had "left a huge hole".

"He was such a major part of our lives that we will never be able to replace. We hope that no other family ever has to go through what we have been through," he said.