The few kayakers capable of navigating Trout Pool Falls near Rotorua do so when the Kaituna River is at a gentle flow.
Things can get hairy fast on the spitting stretch of whitewater, even in the short, hardened plastic creek boats favoured by extreme paddlers.
Mike Dawson and Vavra Hradilek agree you'd have to be all kinds of mad to run the 5m waterfall at full flow, in 9kg carbon-fibre boats, let alone try and navigate around metal slalom gates in the process. Except lunacy is only valid when you don't have a cunning plan.
When 25-year-old Dawson and 24-year-old Czech master Hradilek made their mind-boggling descent of a flooded, bank-bursting Kaituna recently, they did so with a firm eye on the London Olympics.
"No-one really paddles that part of the river at that sort of flow," Dawson explains, with droll understatement. "If you get stuck and there's no-one there to pull you out, basically you'd have to get fairly creative to get yourself out of the situation. We had a really good safety crew though and we'd minimised the risks but, even then, there was a few nerves.
"And that's exactly what we were after - that apprehension is exactly what you feel when you're competing in big events and hopefully that gives us an advantage in London."
This is Hradilek's fourth visit to New Zealand, meanwhile, using the Antipodean summer to get a jump on his European rivals.
He struck a lasting friendship with Dawson in the junior ranks and is impressed by where the world No49 is heading.
"Mike's really stepped it up and he's getting a lot more consistency with his World Cup results - qualifying at the world championships proved that.
"You could see his confidence growing during the year and he's starting to believe he belongs at that level."
Dawson qualified his boat for London at the world championships in September and will be confirmed in the team alongside fellow Rotorua-based paddler Luuka Jones in the next month.
Hradilek, the world No3, still has to battle through the vigorous Czech selection races in late April but reckons his Kaituna exploits could give him an edge on the punishing Lee Valley whitewater Olympic course.
"It was amazing preparation for London," Hradilek says of their Kaituna exploits.
"It was intensely physical and needed a lot of technical skill but also in the back of your mind, there was also a mental struggle to overcome.
"I had some real nerves before going off the waterfall and you only get that sort of feeling in really big races."
The pair are racing the New Zealand Open near Palmerston North this weekend, the first of three ICF ranking races, which also take in next month's Australian and Oceania Opens.
Their fearless Olympic build-up is in marked contrast to Jones, who has been treading a more conservative path as she eyes her second Olympiad. The 23-year-old was still a rookie teenager when she qualified late for Beijing four years ago and that inexperience showed, finishing last in China.
"I don't even like to think about where I was four years ago," Jones says. "I've just made huge improvements everywhere - things like halving my skin-fold measurements and being able to fit in two training sessions and a gym session in a day. I struggled to do that even last year.
"In saying that, if I hadn't paddled at the Olympics four years ago, I don't know if I'd still be in the sport today. That experience really increased my profile and opportunities and it was a huge boost."
By qualifying nearly 11 months ahead of the Olympics this time around, she's given herself the luxury of training through the national selection events and only having to peak in the middle of the year.
Dawson and Jones are likely to be joined in London by Tauranga's Ella Nicholas, who will represent the Cook Islands in K1, while a handful of Kiwis still have outside chances to qualify for London in the C1 class.