A St Clair father-of-two and his siblings hope to create history when they swim across the English Channel next year.
Paul Hill, brother Luke and sister Tania aim to become the first three siblings to complete the treacherous 41 kilometre stretch, tackling jellyfish, hypothermia and seasickness.
The Hills hope to raise $500,000 for The Cancer Council.
Their mother, Roma Gai, lost her battle with cervical cancer in 1992 and father David had a 10-year battle with bowel cancer.
"I would love to help at least one family not go through what I did when I was 18," Paul said.
"My sister was 11 and I can't imagine how she felt."
The siblings came up with the idea of the gruelling challenge a few years ago.
"I was a little apprehensive at first, having been out of the water for so long," Paul said.
Once a month Paul travels to the Central Coast where his siblings live to do an open water swim.
The Hills have juggled barbecue and cake stall fund-raisers with intense training, full-time work and family commitments.
They have raised $12,000 and will add more when Luke does 12 hours in a swim spa at Martin Place on Thursday.
Their father David hopes to make the trip to cheer his kids on what will be his first overseas trip.
"He doesn't like flying but has been very supportive," Paul said. "Cancer has made me realise how fortunate I am and I try to make the most of every day.
"I turned 40 last Friday. Mum died when she was 47. Life goes by and changes so quickly."