A coroner is calling for a law change to ban swimming at a popular Taupō rapids after a young woman drowned trying to help a friend.

Coroner Wallace Bain believes another tragedy is likely unless more action than the present warning signs and sirens are put in place around Aratiatia Rapids.

Rachael De Jong, 21, was swimming with six friends in the Waikato River downstream from the Aratiatia Dam when the dam's floodgates opened at midday on February 6, 2017.

Some of the group perched on a small rock were swept away in the rapidly flowing water.

De Jong tried to help a friend but was swept downstream and drowned.

Her body was later recovered.

Supplied The Aratiatia Rapids photographed at 12 noon the day De Jong died, and then five minutes later after the dam was opened.

The dam gates, operated by Mercury, are opened four times a day for tourists. Water flows down the rapids for 10-15 minutes.

READ MORE:

* Spill cancelled, saves swimming teenagers

* Tourist water spill at Aratiatia Rapids to resume, after drowning

* Waikato River drowning victim 'could cheer anyone up' - brother

* Horrified tourists watch swimmers desperately try to save each other

The group were swimming in what the Coroner described as idyllic still waters around 11am and evidence shows a group of five of them were taking a selfie using a Go-Pro stick.

But once the dam was opened the calm swimming hole turned to turbulent surf.

In his findings released recently, Bain focused on the following fundamental question: "How was it that a group of young adults, intelligent, law abiding and very successful in their own lives, were able to access the swimming area, in part read some signs but certainly hear the sirens and still swim in the area at the more dangerous time?".

Bain said the group was not aware of the dangers posed by the Aratiatia Rapids.

PAMELA WADE Coroner Wallace Bain is calling for a law change to ban swimming below the dam.

"The evidence is clear that the group had not experienced anything like this before and had no understanding at all, despite signage and warning signs, as to what they were about to be subject to and the turbulence, force of the water and the washing machine effect on your body if you were in it," Bain said.

"Many heard the [warning] sirens but again, did not understand or fully understand what was about to occur and when."

Photos taken by the group show the rapids approaching in the background, Bain said.

"But clearly the group had no idea of what to expect and did not appreciate the risks, which if you had not been to the area before, it is totally understandable."

Bain said there should have been signage advising the group of the dangerous rapids at the point they entered an unofficial, but well-worn walking track to the swimming hole. However, the signage had been vandalised.

Signage in other places on the track warned of the rapids' danger, but Bain questioned whether the signs were effective.

"Was the signage explicit enough at the time? Signage drew attention to a "risk of drowning", "swimming not advised", "water level may rise", "strong currents and undertow"," he said.

"The warning signs simply do not make it clear enough what is to be expected, particularly to people who have never seen this before," he said.

"New signage emphasises the risk of drowning and that the water will rise rapidly and that it is a prohibited zone."

After the incident, Mercury met with the Department of Conservation and installed additional signage and a wooden barrier on the unofficial track with the aim of preventing that track being used. DOC also removed ropes from the steep terrain which assisted the group in reaching the pool.

A fence has been installed stopping access to the unofficial track to the swimming hole.

While some of the group were aware of the flood gates opening they didn't know what this meant and had never seen it transpire.

As they had taken an unofficial track, the group had circumnavigated the signage. A sign on the unofficial track was stolen two weeks before.

Mercury, which operates the dam, has a six-monthly hazard review for the site, Bain said. The warning sirens are regularly checked.

Waikato Regional Council considered a bylaw to regulate swimming in the area but independent legal advice stated it wasn't appropriate.

Freedom of entry and access to reserves, such as the land surrounding the Aratiatia Rapids, is granted to the public under the Reserves Act 1977.

However, this could be changed, Bain said.

"The Court strongly recommends....that consideration be given to whether legislative change is necessary to enable a total prohibition of swimming in the area," he said.

"It is clear to the court, that a tragedy similar to this is likely to occur in the future despite the presence of signs and sirens and other measures.

"If the group that were caught on this occasion were not able to sense the imminent danger with all that was then in place then it is clearly possible that this could occur again, especially as it is a tourist area."

He urged Waikato Regional Council, DOC and Mercury to meet urgently to discuss how a ban on swimming in the area while tourist spills continue to occur.

Department of Conservation North Island Director of Operations Allan Munn said the department was set to meet with Mercury and Waikato Regional Council in the next few weeks to discuss what further steps could be undertaken.

Since De Jong's death, Munn said DOC had implemented a range of measures including a barrier on the scenic reserve to stop access to that area.

"Given the Coroner's recommendation we're going to take that to the next step now and look at what else we can do."

Changing the 'scenic reserve' classification of the land accessible to the river had a raft of implications, he said.

"Given we have tens of thousands of reserves alongside potentially dangerous rivers.

"The uniqueness is the spilling is a human induced event that makes a benign piece of water a very dangerous one in a short space of time."

MP for Taupō, Louise Upston, said she believed there could be a case for changing the law.

"I am keen to look at the options and work with Waikato Regional Council, DOC and Mercury to see what could be done," she said.

"This could be done through a Government or Members Bill, which I am open to looking at."

* Comments on this article have now closed