Tracey Lithgow Collins jumps out of the freezing cold water with a huge smile spread across her face.
It's the fourth time she has completed a Heart Stopper Challenge, which raises money for Heart Kids New Zealand.
The cause affects her personally as her 5-year-old son, Kalen Collins, is a heart kid.
He was born with a heart defect and has had three major surgeries in his short life.
"We didn't know Kalen had a defect until he was three, so it was really hard," she said.