All Black great Ian Jones is among a group of middle-aged men who plan to swim from Great Barrier Island to Takapuna.
The group of five friends are motivating each other to carry out the challenge of pulling off the 100km swim across Auckland's Hauraki Gulf.
They've given themselves 24 hours to do it.
The group will swim relay style and are aiming to raise money for St John New Zealand.
Seven Sharp's Michael Holland went along to see how preparations were going in the video above.