An Australian kayaker has plunged more than 20 metres in a daring, hold-your-breath drop down the Dangar Falls in NSW, in the first known paddle of the famous waterfall.

Lachie Carracher, 29, was preparing for the moment for eight months, or realistically, for the 14 years he has kayaked the rivers of the world.

Lachie Carracher (left) was the first kayaker to descend the Dangar Falls. ( Supplied: Lachie Carracher )

He checked out the falls when the river was running low last winter, and kept a close watch on rainfall on the region, ready for the river to hit its peak.

It is not easy to paddle the waterfalls of Australia; the best conditions are found elsewhere, in the wild rivers of South and Central America, rivers that come from the rainforests of the Amazon, not the driest continent on Earth, Carracher said.

"The easy bit is paddling the drop, you just have to be lucky with the weather," he said.

Last week, as Carracher observed the heavy rain in the region and the river peaking, he drove the 15 hours from Melbourne to the falls near Dorrigo, about 50 kilometres west as-the-crow-flies of Coffs Harbour.

On Friday, he prepared to paddle over the falls, which is just a bit more than 20m high and had never been paddled before.

Dangar drop a risky descent

The Dangar Falls has a notorious history. It used to be a popular spot for jumping swimmers, with tourists flocking to the area to make the leap despite council signs warning "Do not jump".

In 2012, a German tourist lost her life after jumping the 20m into the pool at the bottom of the falls. She was found later by police divers further down the Bielsdown River.

Carracher said he was not going into the drop recklessly.

"I don't want to go out and endanger my life," he said.

Dangar Falls is Australia's highest waterfalls able to be paddled, experienced kayaker Lachie Carracher says. ( Supplied: Di Lymbury )

"This isn't a 'try it at home' stunt. It's a very calculated risk.

"I just run it over and over in my head, I've gone over every scenario of 'what are you going to do if it gets out of control?'.

"By the time I'm at the lip I'm completely calm and completely focused."

17 seconds underwater

At times, Carracher worried the storm rain was not enough to make for a safe descent on the falls.

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"There was a lot of deliberation over whether I really wanted it that bad and whether the potential consequences, which grow exponentially with less water, were worth the risk and that's the big conundrum when it comes to running a big rapid or big waterfall.

"It's a large impact when you hit the water … if you have a bad line then your kayak comes off and you get out of control in freefall then it's very likely that you break your back."

He decided to make the drop as a "calculated risk", with a safety team at the bottom.

As he went over, he kept his eye on his landing spot and threw his paddle away from his body so it didn't hurt him on impact.

In the foam at the bottom, he stayed underwater for longer than was comfortable for the watcher — a full 17 seconds submerged — before a support kayaker reached him and helped him to the surface.

That was part of the plan, said Carracher, with rolls up more difficult to do without a paddle.

"If I had been unconscious, he would have been able to get me out of the water."

Anyway, Carracher has been training for it, and can hold his breath for up to five minutes.

'It's not worth breaking your back'

Carracher said this was not the highest waterfall he had paddled, but it did feel like a great achievement.

"When I began kayaking Dangar Falls would have been the world record but it's progressed a lot over the years," he said.

"It's always about risk versus reward … I definitely had voices in my head that I wasn't going to do it and I should just wait for the next storm, it's not worth breaking your back, but then I just saw it was definitely doable and I had the skills to have a safe descent."

Lachie Carracher took this photo of a woman in the Ganges River, which will be shown in the exhibition Ganga. ( Supplied: Lachie Carracher )

With this project complete, another rivers project is nearing its own daring drop, with the photographer's exhibition of his 2,500-kilometre trip down the Ganges River in South Asia coming up.

"I work predominantly as a photographer and design my work around my passion, which is the river, so when I'm taking photos I go paddling," Carracher said.

The exhibition, in aid of a water health centre in Gujarat Province of western India, opens at the Rokeby Gallery in Collingwood, Victoria, on April 6.