Bacon butties are off the menu for 70-year-old Tony Williams, who will go head-to-head with his daughter in this year's Harbour Crossing swim.
Mr Williams, visiting from Britain, is taking part in tomorrow's event, which is raising money for research into children's diabetes.
His daughter, Auckland nurse Helen Greenaway, is also swimming and hopes to beat her father at what is very much his sport, she said.
"Swimming is and has always been his thing and so I'm hoping I just come in at a respectable time."
And she is making sure her father's secret weapon - a bacon sandwich - will be nowhere to be seen tomorrow morning.
"I've told Dad he'll barely have time to get his togs on and he won't be allowed his favourite bacon butty beforehand, otherwise he'll beat me."
Hundreds of competitors will swim 2.9km from Quinton Park across the Auckland Harbour in the State Harbour Crossing.
Mr Williams swam competitively in Europe as a young man. In 2010, while visiting his daughter and family here, he decided to take part in the Harbour Crossing and asked his daughter to join him.
"I wasn't fit enough to do it - and that didn't fit well with me," Mrs Greenaway said.
"Since then I've been motivated to do it. I've been training hard for this."
Mr Williams said he was looking forward to swimming alongside his daughter, especially as they were doing it to raise money for the Juvenile Diabetes Research Foundation.
"We have a young family member, Oliver, who was diagnosed with type one diabetes when he was just two years old," he said.
"The research work is quite fantastic and it's making progress and helping people everywhere."
The father and daughter team have raised just over $1200. Mr Williams has also raised £8000 ($15,600) while taking part in several triathlons in the UK.
"Once you're in the water, you want to do your best. In this case though, we're doing it for a cause so I really do want to give a go," Mr Williams said.
*To donate: http://uk.virginmoneygiving.com and search for Anthony Williams - AucklandSwimChallenge's Fundraising Page