Joseph Parker traded his boxing gloves for a pair of swimming togs today, taking part in the Heart Kids 360 Heart Stopper challenge to raise money for the charity.
Parker is used to taking heat in the middle of the ring but instead spent six minutes in icy cold water to raise money for the Heart Kids Annual Appeal. He raised $43,000 for the charity.
Twelve babies are born with a heart defect in New Zealand every week and it is the number one cause of death in infants and babies.
Joseph Parker said he had a personal connection to Heart Kids because a friend's child was born with a congenital heart defect.
"Getting in the ring with Dillian (Whyte) was nothing compared to this," he said.
"This is just a small thing I can do to raise awareness for a charity that does big things for these born fighters. I'm also mindful that rates of rheumatic heart disease are far too high, especially in Maori and Pasifika communities."
Suzy Cato, Matt Tatton-Brown, David Seymour, Marama Fox and Roger Farrelly also took part in the challenge which represents how the heart is sometimes packed with ice during a heart operation.
Heart Kids provides practical and emotional support to help its 8000 members cope with the immediate and ongoing challenges of living with a heart condition. Its membership is growing by 15 per cent each year.