Authorities have threatened to close the Tweed's Clarrie Hall Dam in northern New South Wales after videos of young people using body boards to surf down a dangerous 110-metre concrete chute emerged on social media.
The video, which was originally filmed in May 2016, was shared on a Facebook page called 'Culturetrip' on 25 September. The clip shows young people on the "illegal water slide".
The video has gained more than 40,000 likes and reactions, and more than 3.8 million views, prompting officials to issue a warning.
Tweed Shire Council's manager of water, Anthony Burnham told the ABC news, that surfing at the chute comes with a serious risk of drowning.
"It's got a large flip bucket at the end which is an energy dissipating device and with any significant flow you can be held underwater in that flip bucket and drowned, obviously on the way down you can be rendered unconscious and drown," Burnham told the news outlet.
The spillway chute is lined with six-metre to eight-metre high walls. It narrows to only 12 metres across its length.
The council would never give permission because of the serious risks involved with a flip-bucket at the bottom of the chute, Burnham said.
The council is also considering its options to stop the illegal surfing practice, which has only worsened after people started posting videos on social media, attracting more young people to the dam, Burnham added.
The video caption states, "Daredevils are using this dam as an illegal water slide. Make sure you seek permission first."
Burnham said the council is going to use CCTV to stop the practice and is also considering a public closure of the Clarrie Hall dam.