Harris, who is recuperating from an ankle injury suffered during his starting debut for the All Blacks against the USA late last year, says he has followed James' story with great interest and was keen to help however he could.
"I mentioned that I was planning on doing the swim to Phil and Toni and they both jumped on board straight away," Harris said.
Growing up in Te Puke, Harris spent as much time on the beach and in the water as he did kicking a rugby ball around with his mates.
He was a lifeguard at Papamoa Surf Club and was highly competitive in the canoe events and beach sprints for his club at local and national surf carnivals.
"There actually wasn't too much swimming involved back then," he said.
"I tried to do the swim from Motiti to Maketu when I was 13 but I didn't complete it. I got about halfway.
"Now my extra weight is a bit of an issue as I am about 110kg so I have had to invest in a good-sized wetsuit that makes me a bit more buoyant," Harris said.
"I was thinking of doing it all myself but with my foot I needed to take it easy. Sharks might nibble on the end of your foot and you don't want that so I put the relay together to improve my chances."
The fundraising swim is a feature of the Maketu Fun Day beginning at 9.30am at the Maketu Surf Club.
The Chiefs guys encourage the public to come down and show their support.
There will be a DJ, ice creams, sausage sizzle, bouncy castle and sports memorabilia auctions.
-To support the Chiefs' entry into the race and donate to the James Reid cause go to www. givealittle.co.nz/cause/TeamJames