A New Zealand man behind an ambitious crowdfunding campaign that raised millions of dollars to buy a privately-owned South Island beach said on Friday he was stunned at its success.

Duane Major's push to take Awaroa beach out of private hands and make it a national park quickly went viral, attracting 40,000 donations to raise a total of NZ$2.3mn (US$1.6mn).

Major, a pastor who describes himself as "an ordinary bloke", called the response to his givealittle.co.nz page as heartwarming.

"I always thought we could do it but I didn't anticipate what a crazy, heartwarming ride it would be," he told AFP.

"It's really tapped into a community spirit among New Zealanders. I've been getting poems from schoolkids talking about our beach. It gives me goosebumps."

Awaroa inlet is an 800-metre stretch of golden sand adjoining the Abel Tasman National Park at the top of South Island.

Accessible only by boat or helicopter, it came on the market late last year, with real estate agents marketing it as "the best beach on the planet".

Major decided after discussions with relatives over the Christmas period that a crowdfunding page was "certainly worth a shot".

Tens of thousands of New Zealanders agreed, and Givealittle said it had become the country's largest ever crowdfunding effort, raising more than NZ$1.0mn in a single day.

"It's the largest campaign we've facilitated by a long way," a spokeswoman told AFP.

Major said donations ranged from children giving a dollar to corporations pledging tens of thousands.

The government chipped in NZ$350,000 earlier this week to get the campaign over the line and the tender offer was formally accepted on Wednesday.

Major said he was overjoyed at preserving "a slice of paradise" for future generations and was already considering more crowdfunding conservation campaigns.

"We were celebrating last night and I was yakking (talking) to a guy with a big beard called Mike and he said 'wouldn't it be good to do it again?'," he said.

"I told him I'm just trying to catch my breath now, but I could feel the energy coming back."