Procedures for opening a dam on the Waikato River are being reviewed after 21-year-old Rachael Louise De Jong was swept to her death in its surging rapids yesterday.
Three of those in the group she was swimming with made it to the safety of the river's banks after Aratiatia Dam opened at midday yesterday. The Police Dive Squad recovered Ms De Jong's body last night.
The dam, which is north of Taupō, is opened four times a day in summer to allow tourists to see the river in full force.
Taupō mayor David Trewavas said locals were devastated by the drowning.
"A group of people in their 20s went for a swim below Aratiatia Dam, and the dam opens and the pools fill up very quickly, obviously, with the water flow down the Waikato River.
"So unfortunately on such a beautiful Taupō day where everybody's in the water, these young people have gone for a swim and decided to stay in a bit long by the sound of it."
Mercury Energy operates the dam and has suspended its opening after the drowning.
Its chief executive, Fraser Whineray, said they were saddened by Ms De Jong's death at the popular tourist spot and were looking at ways to improve systems.
"The sirens are working, they go four times before a spill, and the signage is there to request that people do not swim in that area, but certainly we have to ... make sure that the risks ... are minimised to the greatest extent that we can."
Dave Kilmister owns Huka Falls River Cruise, which operates upstream from the dam. He believed the current warning systems did a good job.
"They normally have a warning siren at about eight minutes to, and another one at three minutes to the hour and then another one right on the opening time, which is a longer one, so you know you can hear them a long way down the rapids."
Mr Kilmister said while swimming in the area was not common, photos posted on social media spurred more people to jump in after dam openings.
He said he would not recommend that.
"The rapids are opened purely to show the public what the river used to flow like. They have a rate of about 65,000 litres of water a second going through so it's a big lot of water.
"Obviously if you go in there you're putting yourself at risk."
And while the scheduled dam openings for tourists are suspended following the drowning, Mr Whineray is warning people to continue to be wary.
"Everyone should always treat the rapids as live because the spillway doesn't just operate for tourist purposes.
"It can operate for things like flood management and letting the water that actually comes down the Huka Falls through down the rest of the Waikato River, so we'd really ask please if people could not be down in the rapids area because it can be very dangerous when those spillways are open for all the obvious reasons."
Mr Whineray said he was not aware of any previous fatalities on the Aratiatia Rapids.
Mr Trewavas said aside from a close call in 2009, there had been few incidents at the dam.
Ms De Jong's death will be referred to the coroner.