She will be raising money for the Darryl Fairbairn Memorial Fund to provide counselling and support for children and families in Upper Clutha who have gone through trauma and grief.
Darryl Fairbairn, who died in 2005, leaving behind his young son Finn, was a man who "always helped people".
It's a whopping distance; to put it in perspective, Cook Strait is about 22.5km across, Foveaux Strait is wider that that by 3.2km and Lake Taupo is 40.2km.
Mrs Fairbairn (48) believed "pure grit and determination" would get her through the swim, which she expected to complete in between 15 and 17 hours.
The Fairbairn family were living in Christchurch when Mr Fairbairn died, and Mrs Fairbairn and Finn (now 21) later shifted to Wanaka.
Moving to Upper Clutha, she was concerned there nothing in the area to support children and their families going through difficult times.
In 2007 and again in 2017, Mrs Fairbairn and some friends swam the length of the lake - from Makarora to Wanaka - in a relay, taking 13 hours, and the money they raised went to the fund.
When she was diagnosed with dangerously high blood pressure and told she could not do anything until it was under control, she was not used to "sitting on the couch".
So when she was finally able to get back into exercise, she still was not particularly motivated and needed a goal.
Due to the large number of people accessing the fund - particularly in the last year - she realised it would need a regular top-up if it was going to continue helping people.
So she decided to attempt to swim the lake by herself, rather than in a relay. At that stage, the furthest she had ever swum in open water at any one time was 4km but she was now up to 12km.
Her plan was to swim for 18 minutes then have a "feed stop" for two minutes while treading water.
"They'll be throwing me food, I've been trialling that a lot," she said.
Mrs Fairbairn expected the biggest challenges to be the cold, tiredness, sore shoulders and the weather.
When it came to conditions, she was going regardless - as long as her safety adviser said she could go. "I'm hoping for a nor'wester, rather than a southerly," she said with a laugh.
As for the delicate question of answering the call of nature, Mrs Fairbairn said she had designed the type of food she was eating during the swim to hopefully help with that.
"Instead of just existing on a liquid died of sports drinks and gels, I am also having some food with fibre, protein and fat to hopefully slow the rate through my gut," she said.
And as for what her family thought of her epic challenge? "Finn thinks I'm a bit of a legend ... Darryl would think it would be just like me."
