O'Callaghan goes low in 200m Olympics tune-up

Mollie O'Callaghan has responded to Ariarne Titmus's stern challenge and stolen the year's fastest 200m freestyle time from Canada's Summer McIntosh in a pre-Olympics statement on the Gold Coast.

The world-title holder won the Australian championship on Saturday night, touching in one minute 53.57 seconds ahead of Tokyo Olympic champion Titmus (1:55.38).

O'Callaghan wasn't overjoyed with her time despite it being the quickest in the world this season, beating Canadian star McIntosh's 1:54.21 effort just 10 days ago.

The 20-year-old was pushed early by sprint specialist Shayna Jack, who won the 50m freestyle earlier in the meet, before Titmus came with 75 metres to swim.

But O'Callaghan surged clear after the final turn to win by more than a body length, Titmus backing up from a sub-four minute 400m victory on Friday.

The championships will be O'Callaghan's last competitive racing before June's Olympic trials in Brisbane.

"I'm always striving to go faster. The 200 is a very difficult event to work out and this was the last time to get it sorted before trials," O'Callaghan told Channel Nine.

Kaylee McKeown was on her own world-record pace early in the 200m backstroke final, her time of 2:03.84 just 0.7 seconds slower than her 2023 high mark and more than five seconds quicker than the rest of Saturday's field.

Emma McKeon, Australia's most decorated Olympian, won the 100m butterfly in pouring rain, clocking 56.58 ahead of Brianna Throssell (56.77) and Alexandria Perkins (57.73).

"I just want to see what I'm capable of, both mentally and physically, and that's what keeps me going," McKeon said.

Rio Olympic champion and Tokyo Games silver medallist Kyle Chalmers dominated the men's 100m freestyle, winning in 47.63 ahead of William Yang (48.20) and Kai Taylor (48.69).

Recently crowned 50m breaststroke world champion Sam Williamson (27.16) held off Josh Yong (27.60) to claim the national title in an event that isn't raced at the Olympics.

Japan's former world champion Daiya Seto, training under Michael Bohl at Griffith University, beat New Zealand's current global title-holder Lewis Clareburt in the 400m individual medley.