He stops short of labelling it a mid-life crisis, but Craig Stephenson admits he was looking for a new challenge in his life.
Not one to do things by halves, the Taupo father-of-four has set himself the goal of swimming the 320km length of the Waikato River from Taupo to Port Waikato in March.
Mr Stephenson said the idea first came to him about a year ago and at first he didn't think it was the sort of thing a working family man could do.
"But then I read Kevin Biggar's book The Oarsome Adventures of a Fat Boy Rower about how he rowed across the Atlantic Ocean and he was a nobody with no athletic prowess ... and some of the things he was saying, it kind of got through my head that you don't have to be like Superman to do these things.
"And then it was just kind of one of those moments when I thought why not? Let's do it."
But his mission is much more than just an epic swim. He is also concerned about the river's health and access to clean water generally. On a family trip to South Africa this year he realised that safe drinking water is an issue for many people, particularly in the Third World.
So he decided to seek donations for the swim, to be donated to Unicef, which has a programme to provide clean drinking water for children. He's aiming to raise $10,000.
Mr Stephenson plans to leave from Taupo on March 11 and hopes to swim the length of the river in 10 days, although there are some bits he'll have to walk around, including Huka Falls and the hydroelectric dams. He said river flows would be low at that time of year and he could not rely on help from the current, which was often non-existent.
"You've got the big long hydro lakes in the upper reaches and it'll be like swimming from here to the other end of Lake Taupo."
He also plans to swim alone for much of the way, towing a small bag with essential supplies and without a support boat or kayaker, although he'll use one on busy stretches such as Lake Karapiro. He'll meet his support crew at the end of each day and his family will join him on weekends.
"I was looking for something to do, something hard. Life's pretty soft most of the time, we've got it pretty easy in New Zealand so I thought let's do something difficult," he said.
Mr Stephenson's mission is the second known attempt to swim the Waikato River. Melbourne-based New Zealander Paul Percy completed a similar swim in 2003.
You can support Mr Stephenson by going on to unicefchampions.org.nz/cause/waiswim13 and donating any amount. He also plans to keep a blog during his epic swim.