McMillan (29), who grew up in Cromwell, has represented the New Zealand side since 2008 and captained it to glory in the last world championship in Adelaide in 2012.
Despite living in Auckland and teaching at St Peter's College, he will represent St Clair during the championship in Montpellier.
McMillan, who first joined the St Clair club in 2002, is the only member of the 12-strong team representing a South Island surf life-saving club.
He is confident New Zealand can defend its crown.
''We have got such a strong group with a lot of experience.
We have got three [new team members] this time round, but it's great to see the new blood coming through.
''We have a really good team culture and we are all really good mates. If we can do the individual pieces right we can get one hand on the trophy and bring it home, hopefully,'' he said.
McMillan is no stranger to competing on the big stage. He represented New Zealand in swimming at the 2012 London Olympics as a member of the 4x100m medley relay team.
He attended Otago Boys' High School as a teenager, before studying at the University of Otago from 2003 to 2007 and graduating with a degree in physical education in 2010.
A couple of years after knocking over Australia on home soil, McMillan said the team from across the Tasman would be the biggest challenge in the south of France.
''Australia are our main rivals and usually the hardest team to beat. Coming off a home loss in 2012 they will be ready. They have poured a lot of resources into [this campaign].''
France and Germany would also pose strong challenges, especially France in front of a home crowd, he said.
With less than four weeks until the competition begins, the team flies out to the Gold Coast tomorrow for a second training camp.
During the first camp a fortnight ago, Willie Apiata, the first and only Kiwi to be awarded the Victoria Cross for New Zealand, spoke to the team.
''He was amazing,'' McMillan said.
''He shared some cool stories and underlined the same values we have as a team.
''To hear the same values that a lot of us New Zealanders share and to hear the things that push our buttons and get us fired up was really good.''
All Black coach Steve Hanson and All Black lock Sam Whitelock also spoke to the team.
The Kiwis will return from the Gold Coast for the New Zealand Pool Championships in Auckland starting on August 29.
McMillan said the team would use the event to get rid of any rust before departing for Europe.
''We will look to blow some cobwebs out of the system and see what's working and what areas to improve on.''
Outside of the training camps, McMillan's weekly individual training involved five swims, two runs, three gym sessions and one yoga session.
As for getting back to Otago to visit friends and family, teaching, training and coaching commitments with the Parnell Swimming club meant visits were few and far between.
However, representing St Clair was something McMillan wanted to do as much as possible.
''I don't know how much longer I have got left at the elite level but I will compete as much as I can. The thing I love about it is that it's doing a service for New Zealand beach safety. It's giving back to the club and surrounding regions,'' he said.
The Black Fins begin their title defence on September 16.
- by Robert Van Royen
