Budapest - Defending champion Bronte Campbell is braced for a "fist-fight" in the 100m freestyle semi-finals after a flurry of fast times from top names in the heats on Thursday.
Just as in the men's race, the women's blue riband event is shaping up to be a fierce scrap in the pool at the world aquatics championships.
Sweden's Sarah Sjostrom, who set a new world record of 51.71secs in Budapest on Sunday, was fastest in the morning heats, clocking 53.01secs.
Australia's Campbell, the world gold medallist in the 50m and 100m freestyle in Kazan two years ago, was eighth fastest, but just 0.55 behind Sjostrom.
"It's nice not to have to go at maximum speed, but tonight it's going to be a fist fight to get into the final," said Campbell.
Sjostrom, who won the 100m butterfly gold on Monday, was happy to be back competing "after two days off".
"I had the speed from the start, but there's no point in going for it, so I just kept the momentum up," she said.
Simone Manuel of the United States and Canada's Penny Oleksiak, the joint Olympic gold medallists from the Rio Olympics, were at 0.71 and 0.79 back respectively.
Dutch sprinter Ranomi Kromowidjojo, the 2012 Olympic champion, was sixth fastest at 0.44, while Australia's Emma McKeon was at 0.46.
McKeon, who has already won four silvers in the 200m freestyle, 100m butterfly, 4x100m freestyle and mixed 4x100m medley, is battling fatigue and her rivals.
"It felt quite comfortable, but that was my ninth race," said the 23-year-old.
"I knew that this morning, it would be quite challenging to get myself going.
"I was set a different warm up this morning and it helped to refresh my mind."
Defending champion Mitch Larkin of Australia squeezed into the men's 200m backstroke semis as 13th fastest at 1.89secs behind Ryan Murphy, the Olympic champion, the quickest who clocked 1.56.11.
Larkin said his slow time was all part of the plan.
"I felt pretty groovy, I had a fair bit left in the last 50 metres and could have lifted it at a little bit, but felt I was in a good spot," he said.
China's Xu Jiayu, who won the men's 100m backstroke gold on Tuesday in Budapest, was the fifth fastest at 0.81secs behind Murphy.
"It was good, I'm trying to move through these heats as easy as possible," said Murphy.
Having set a new world record in the women's 100m breaststroke on Tuesday, 20-year-old Lilly King of the USA was second fastest into Thursday's semi-finals over 200m at 0.25 sec, behind Britain's Molly Renshaw, who clocked 2:24.03.
Australia's Taylor McKeown, the 2014 Commonwealth champion, was third fastest at 0.28.
With breaststroke sensation Adam Peaty opting not to contest the 200m, Anton Chupkov of Russia was the fastest into Thursday's semis at 2:08.73 with Britain's Ross Murdoch at 0.75 back.
Germany's Marco Koch, the defending world champion, was 13th fastest at 2.17, while Olympic champion, Dmitriy Balandin of Kazakhstan was 10th quickest at 1.95.
In the heat's for Thursday night's 4x200m freestyle final, China clocked the fastest time of 7:51.75 with Japan, the United States and Australia also safely through.