"Being the navy and the travelling aspects, I don't think distance is a problem for us - we're used to travelling distances.
"We actually missed the last World Masters Games, because they were in Europe. They were on our doorstep, so we didn't bother.
"The further away from the UK, the better."
The 15-strong team is a mix of serving naval personnel, ex-servicemen and women, and their relatives. Mittins, whose husband Dick served in the navy for 25 years, is the oldest at 67.
"In my case, we used to live in Australia and still have family in New Zealand, so as soon as they announced the Games would be here, I registered," she says.
Running April 21-30, the Masters Games will be contested over 28 sports and 48 venues, and for Thomas, who has medaled in his age group at three previous Games, that diversity makes this event special.
"This is a totally different environment to a specific swimming competition," he says. "We have world masters swimming championships, where everyone talks about swimming.
"You get bored of it, you spend your whole life in a swimming pool ... it's just swimming, swimming, swimming.
"When you come here, there's such a variety of athletes, the ages, the friendliness of it all ... it's just one of those competitions that people want to come back to. We're already saving for the next one in Japan."
While Thomas is driven to medal again, and add to his swag of one gold, six silver and three bronze, he's also wary of the calibre of opposition he's up against in the pool.
'You're swimming against people who have been to the top," he says. "In my age group, there's a guy named Richard Lockhart, a Kiwi, who went to the Seoul Olympics and is still outstandingly fit.
"He's going to do a job here in his own country, and I think, more and more, athletes that get past their mainstream competition ages will look at events like this and you'll see more people remain involved."
Mittins' aspirations are far more conservative.
"If I'm honest I've had a few little health issues that have set me back a bit, so I want to thoroughly enjoy it, still do my best, but not be disqualified, so at least I have some street cred," says Mittins.
"For things like the relays, even if you're on death's door, you still go flat out."
World Masters Games 2017 pool swimming events will take place at the Sir Owen G Glenn National Aquatic Centre, AUT Millennium, Mairangi Bay.