One minute, he's a fun-loving dad, enjoying his paternal duties with the little light of his life, 11-month old daughter Astrid; the next, he's got to metamorphose into 'Big Tuna' mode, a veritable killer of the pool again.
Little wonder the mighty Kyle Chalmers admits it's not easy wrestling with his split personalities as he homes in on a landmark Commonwealth Games achievement.
In his third and almost certainly final Games, the 28-year-old Dolphin-in-chief, with two relay golds and a 50th major international medal already under his belt in Glasgow, admits he's in a competition like no other in his garlanded career.
His first Games was in a home pool in the Gold Coast, where he began as Olympic 100m freestyle champion but found the pressure and expectation made it hard to savour.
The second in Birmingham 2022 was "challenging in its own way" as he had to deal with COVID-19 as well as total disenchantment about what he felt was a media smear campaign over "false clickbait" stories of his relationships with fellow team members Emma McKeon and Cody Simpson.
Glasgow, though, feels like a happier world and a lifetime away.
It's been both a chore and a delight as he reflects on an 11-month journey just to be in the unlikely position of being 'superdad', aiming at becoming the most bemedalled Australian male swimmer ever at the Games.
"For a start, it's my first time racing as a father, so that's exciting," Chalmers says.
"And having my daughter (Astrid) and wife (Norwegian swimmer Ingeborg Loyning) here in the crowd is special.
View this post on Instagram
"Being able to navigate the last 11 months to get to this point of training, as well as being up all night, sleep deprived, it's been challenging.
"It's just getting to enjoy that experience for the first time with them.
"I'm still on dad duties while I'm here, like I'm looking after my daughter while my wife trains because she's got the European championships in a couple of weeks' time. So it's an exciting new challenge."
With it, though, comes his new Jekyll and Hyde routine as he sets out on the defence of his 100m free crown, the pool's blue riband event, on Monday.
"I know that I have to change my mindset from being in the hotel room, being that fun, fatherly figure to then going into that arena and trying to find that killer instinct to get the best performance out of myself," he says.
"So I've got to be able to learn how to change that hat really quickly - and I'm lucky that I've got the Commonwealth Games to kind of practice that in the lead up to the 2028 Olympics."
If he makes the Games sound like a mere stepping stone to LA 2028, then he makes no apologies.
"It would be amazing to defend the 100m title, but I've also been able to win it previously and win every title.
"For me, I guess now everything's just the icing on the cake, and I just want to actually enjoy being in the marshalling room with my mates.
"I don't want to go in there with the full expectation and pressure on me. I actually want to be able to go out, look into the crowd, see my wife and daughter, and enjoy that moment I've worked so hard for.
"Because I know previous times when I've been the favourite, and the pressure's been on me, it's quite overwhelming.
"So I think I've now earned my position where I just get to actually enjoy this moment. Being able to defend that title in the 100 freestyle is something I'd love to do, but it's not the be-all-and-end-all for me either."
It's the same with his pursuit of Ian Thorpe's record Commonwealth men's tally of 10 golds and one silver. Chalmers, on nine golds and two silver, now needs to lift the 100m free title to take him past the legend.
"It would be an honour to surpass the greatest male that's ever swum for Australia at a Commonwealth Games," he muses.
"I've been able to achieve so many great things in my career and if I'm able to do that, it would be the icing on the cake.
"But I'm not stressing about it."
