Like many of the 1,700 swimmers who will attempt to navigate Auckland's harbour crossing tomorrow morning, Bronwyn Impson's battle will be as much mental as physical.
"I'm terrified. Absolutely terrified," the 34-year South African-born social worker said.
The 2.9km distance should not be too much of a problem for Ms Impson, who is using the event as a training exercise in the build-up to the Taupo half ironman. But to complete the course - which starts at Bayswater's Quinton Park and finishes at Karanga Plaza in the Viaduct Harbour - she'll have to conquer her fear of the open water.
"Swimming has always been one of those things that I can't do," she said. "I got stuck on a different level of evolution."
Ms Impson's journey to the start line began with a marriage break-up four years ago. She asked two friends who had endured divorces how to get through it.