Reporoa sawmill worker Brad Scrivener has been going to the popular Hot and Cold geothermal pools at Waiotapu for years.
But Monday night's trip left him splashing puddled water and pouring beers over his blistering skin when he was unexpectedly burned.
After spending three hours in Rotorua Hospital he's warning others of collapsed ground at the pools that left him with second-degree burns on his right foot and ankle.
Scrivener was walking through ankle-deep water to stairs on the side of a bank at the pools near Waiotapu when the bottom "just dropped straight down".
The water level was around his knee when lost his footing and stepped again with his right leg into searing water.
"I dropped down to my thigh and it would have gone deeper if my left knee hadn't hit a rock on the way down."
He managed to pivot and pull himself out and turn his phone light on in the "worst pain" he'd ever experienced.
"I wouldn't wish it on my worst enemy," he said.
"I looked down straight away and it was instantly swollen and blistered and nasty."
"We had no cold water or anything ... We found a little puddle and my mate just splashing the water up on my leg."
Then his friends got him straight to hospital.
"We just had a box of Waikatos [Waikato Draughts] in the back so we were just pouring cold beers down my leg."
Scrivener is now home recovering but can't return to work until the burns have healed.
He is concerned about the instability of the ground underneath the natural pools.
"I stood in the same spot two weeks ago and it was solid ground."
He said a friend who witnessed the fall contacted the Rotorua Lakes Council and Scrivener hoped the council would check the site and put up new signs to warn others about going at their own risk.
"I just don't want to see it happen to anyone else, let alone a child."
In response to questions from the Rotorua Daily Post, the council said it had not been able to confirm it was contacted about the burns at the pools.
A spokeswoman said a staff member had been trying to contact Scrivener.
"The location of the swimming area where he was is privately owned, so he may have been referred to the landowners. The area was previously managed by the Department of Conservation.
"Council staff are following up to ensure the landowners are aware of the situation and can take any appropriate action."
Attempts to contact the landowners have been unsuccessful.