She may have set an Olympic record in her first individual race at Rio 2016, but Cate Campbell is finding the late-night schedule difficult to handle.
Campbell was part of Australia's gold-medal winning 4x100 metre freestyle relay team on day one, but Wednesday's 100m freestyle heat represented her first solo outing.
The 24-year-old was in fine form as she added a new Olympic record of 52.78 seconds to the world record of 52.06secs she set in Brisbane in July to advance to the semi-finals fastest.
However, Campbell was seen hitting herself before the race, and when asked why, she replied: "Just trying to wake up to be honest.
"It's still a little weird. We were getting up and it was like 10 in the morning, bleary eyed and there were people out there already running or coming back from their workout and you're like 'ugh'.
"So yeah, just trying to wake up. You're always a little bit nervous for your first swim so I'm really glad that that's out of the way."
Sarah Sjostrom was third fastest in the heats, but, having already won gold in the 100m butterfly and silver in the 200m freestyle, does not believe breaking Campbell's record will be within her capabilities.
"I think the world record in the 100 freestyle is more for Cate Campbell to beat. I can't swim that fast, it's not possible for me," she said.