The 34km swim between Stewart Island and the South Island has been done by 10 people, but never by an Australian.
Wayne Armour is raising money for the millions of animals affected by the Australian bushfires.
The 33-year-old says cold, turbulent and shark-infested water is one of his biggest fears, and hopes to inspire others with his effort.
Based in Christchurch, Armour works as a physiotherapist and had been involved in competitive swimming in his teens and twenties.
He told the Southland Times that he lost his passion for swimming after he stopped competing and gained weight - but with his upcoming challenge he hoped to show that he and others could take control of their lives.
He will be in good company for the journey across the Strait - his friend Chloe Harris, who holds the record for the fastest crossing, will accompany him in an inflatable boat.
