Olympic gold medal prospect Ariarne Titmus eased back from three months out with a shoulder injury Wednesday to clock 1min 56.11sec in the women's 200m freestyle at the Australian national championships.
Despite missing a crucial chunk of training in the lead up to the delayed Tokyo Games, the 20-year-old comfortably won her heat on the opening night at the Gold Coast.
But it was Emma McKeon, who is looking to better the bronze she won in Rio in 2016, who proved quickest, hitting the wall in 1:55.79.
They will face off in the final on Thursday morning, mimicking the schedule in Japan, where heats will also be swum in the evening.
Titmus won silver over 200m at the 2019 world championships in South Korea behind Italian veteran Federica Pellegrini, but it was her stunning upset of seemingly invincible American freestyle great Katie Ledecky over 400m that catapulted her to global attention.
Head coach Rohan Taylor said the nationals, which run until Sunday, were an important barometer on the road to Japan.
"Some may have rested a little bit for this meet, some may not have depending on who they are," he said.
"They'll go home and take stock of the performances, and we'll talk to them and see what kind of support they might need to just continue their preparation to ensure that they get to the Olympics and perform."
Australia holds its Olympic trials in June.
Elsewhere, Olympic 100m freestyle champion Kyle Chalmers posted 1:48.18 in the 200m heats. Like Titmus, he is returning from a shoulder injury. Young prospect Elijah Winnington was fastest in 1:46.89.
Another fast-emerging youngster Kaylee McKeown, who favours the 100 and 200m backstroke, clocked a sizzling 27.52 over 50m ahead of two-time Olympic relay gold medallist Emily Seebohm, who is targeting a fourth Olympics.
Swimming has long been the medal-winning backbone for Australia at the Olympics.
They won 10 medals in the pool at the 2016 Games in Rio, matching their feat from London four years earlier, but well down on the 20 they clinched in Beijing in 2008.