Australian handball player Callum Mouncey was sitting in a pool on the roof of a hotel in Qatar when he made the decision to become a woman.
He dried himself off, went downstairs and sent a Facebook message to his mum, because he wanted her to be the first to know.
Then in May the 26-year-old went to Albury on a Friday as a man and returned on the Sunday to Canberra, where she has lived the past eight years, as a woman.
Now Hannah Mouncey wants not only to raise awareness of transgender people through working with the Pride In Sport program but to represent the country as a woman – potentially becoming the first person to do so in a team sport as a man and a woman.
Last November Mouncey was part of the Australian men's handball team's campaign to try to qualify for this year's Olympic Games.
She had a lot of time on her own to think and the frustration she was feeling became "really overwhelming".
It was then she realised she could never "tour again as a male" and she "had to do something about it".
While some people know they are transgender from a young age, for Mouncey the realisation came relatively late as she worked through some other issues with a psychologist.
Her reasons for transitioning weren't so much about changing her body, it was more about the way she was seen by others.
It's led to her being much more relaxed and has taken her friendships to another, deeper level as a result of her new-found ease.
Mouncey started hormone treatment in November, told her family of her decision – about which she was understandably "very, very nervous" – and came out to everyone else in January before transitioning to a woman two months ago.
She said the response had been "really, really supportive", something not all trans people were lucky enough to have.
"I was never going to transition before telling my mum and I remember one day, it was the back end of the tournament and I was just up in the pool on the roof, I was up there by myself and I thought, 'Why not? What is stopping me from doing anything?'," Mouncey said.
"So I just got up out of the pool, went downstairs and sent her a big long message on Facebook. It was a very quick thing to make the decision.
"It was something I worried about a bit – how I'd do it – because I just didn't want her to be upset, [but] I knew she'd be supportive."
Now Mouncey is hoping to make the Aussie women's handball team.
She said the International Olympic Committee's guidelines were for 12 months of hormone treatment before she could compete in women's sport, but she was hoping to play in a couple of tournaments a month earlier than that.
Her testosterone levels are already below what's considered the required levels.
"I don't know of anyone who has ever done it before – who's been transgender and competed internationally in a team sport, or even at a national level in a team sport, particularly an Olympic sport," Mouncey said of her switch.
"There definitely hasn't been anyone who has gone from a men's national team to a women's national team.
"Because there's no precedent it's going to be a bit difficult, just because you've got to work through legal things as much as anything."