You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
Mr Boult called those involved "idiots" and said people would die if the lockdown was not taken seriously.
Ten people were photographed about 3.30pm standing in swimming costumes on or by the bridge, and a man and a woman were above them, poised ready to jump into the river below.
In a post on its Facebook page, the Queenstown Lakes District Council said such activity was "not acceptable" during lockdown.
"Please don’t do it, for the good of the community, and out of respect for our medical professionals and emergency services."
The council said the picture was taken by a member of the public who contacted Civil Defence Wanaka area co-ordinator Jeff Donaldson, who in turn contacted the police.
The group had left by the time police arrived.
The council later warned people on Facebook about their language and "vitriolic" comments under the post.
Mr Boult said it was "deplorable" that people were not remaining in their bubbles and were possibly causing the community to go through "social and financial pain" for nothing.
"People are going to die. They are putting our frontline medical staff at risk."
He was supportive of the police, but said they were limited in what they could do.
"On the back of this, maybe it is time we start to have a discussion with police at a senior level about tougher ways of dealing with this."
Queenstown currently has the highest concentration of Covid-19 cases in New Zealand.
Mr Boult further warned any kind of clarity concerning when the lockdown would end was impossible for residents in the Queenstown Lakes district.
Despite an abundance of information made available to the public, Mr Boult said his community was understandably very nervous given the uncertainty that lay ahead.
"It’s all very well to have sources of information but there is no answer to when the lockdown will finish ... What good is information when it’s anybody’s best guess?" Mr Boult said.
The mayor, who has been in office since 2016, said the district would be the New Zealand community hit hardest by the wider economic effects of Covid-19.
"No doubt about that, [while] most parts of New Zealand rely on tourism to a certain extent, we rely on it pretty well 100%."
However, he said he had always admired the spirit of the people in Queenstown Lakes.
"Most of us moved here because we love the place, we love the lifestyle it gives us and I’m very confident that we have an enormously resilient community that will recover from this and rise above."
The pandemic had kept Mr Boult working for over two weeks straight, averaging somewhere between 12 and 16 hours a day.
He said he was fortunate to have had previous experience of having to show strong leadership through a crisis.
"I was running Christchurch Airport when the earthquakes struck in 2011.
"‘I know what’s required and what is required is decisions made and a decisive leadership given."