Multisport champion Sam Clark conquers roaring Mokoroa Stream

When the flooding struck Whakatane, sending a raging torrent of water down the Mokoroa Stream, Sam Clark knew what to do - he grabbed a kayak.

He's an Ironman and one of the top Multisport athletes in New Zealand, winning the Coast to Coast race two years in a row.

So despite only paddling whitewater kayaks for six months, he set himself a challenge - to make the first known descent of the roaring Mokoroa Stream.

"Normally it's not much more than a trickle," Mr Clark told Newshub.

"I popped my head over the bank and took a look at the falls and they were going really, really hard so I went back home and called my mate Karl and said: 'I wanted to be the first person to go down over the falls.'"

He collected his gear, safety equipment, a spotter, and took the plunge - all captured on camera.

"This is the first known descent of the Mokoroa Stream," he says in the video.

"A lot of water today. Should be pretty fun."

Mr Clark raced down the white water, only centimetres between the jagged rocks on each side.

He shot around the debris and submerged obstacles underneath him - and came out unscathed.

"I was a little bit apprehensive, but when you're doing something like this you have to commit to it," he says.

"When you hesitate, that's when things go wrong."

Mr Clark says he doesn't encourage others to paddle in flood conditions unless they have a lot of experience, and to never paddle alone.