Serious Fun Riversurfing was established in the summer of 1989 and general manager Neil Harrison said the birthday was a huge milestone for the company.
"I'm extremely proud to be part of Serious Fun's 20-year history. This celebration marks the fact that thousands of people from all around the world have enjoyed an amazing experience on the mighty Kawarau River."
The company's story began when Jon Imhoof, a backpacker from Hawaii, started taking friends bodyboarding on the Kawarau.
"At first it was just a group of mates having a bit of fun on the river then friends of friends starting coming along," Mr Imhoof said.
"In those days tourists and locals hung out together at the old Eichardt's pub, so we were soon taking tourists down the river, too.
"That first summer we offered free trips, accepting any donations along the way.
"Realising that man could not live on beer alone, we acquired the appropriate licences the following summer to become the first commercial riversurfing operation in the world.
"Before we knew it, we had an exciting business under way."
Mr Harrison said the company had built up steadily over the years.
"Today, we have a dedicated crew of 16 guides with whitewater boarding experience from all over the world.
"Only recently we became the first whitewater boarding activity in New Zealand to achieve Qualmark, New Zealand tourism's official mark of quality."
Mr Harrison said Serious Fun Riversurfing had a 100% safety record and was the only operator to offer the longest grade 4 rapid river surfing experience in New Zealand.
"We're really proud of these successes and we'll continue to work to improve our customers experience," he said.
