Australian sprinter Cate Campbell showed off her starting speed Thursday in morning heats of the 100-meter freestyle at the swimming world championships.
Campbell was 0.10 ahead of Britta Steffen's 2009 world record halfway through the race and then cruised in the second lap to set a leading time of 53.24 seconds.
American teenager Missy Franklin qualified second in a personal-best 53.36 as she attempts to extend her perfect record of three golds in three events so far.
Sarah Sjostrom of Sweden advanced third in 53.61, Steffen was fourth in 53.93 and Olympic champion Ranomi Kromowidjojo of the Netherlands was fifth in 54.12.
Steffen's world record is 52.07.
"I think (Campbell) is the top favorite," Kromowidjojo said. "But nobody has really given it their all yet. So we'll see tonight and tomorrow."
In other prelims, Olympic champion Tyler Clary led the men's 200 backstroke in 1:56.76 and American teammate Micah Lawrence topped the women's 200 breaststroke in 2:21.74 -- an event that two-time Olympic champion and world record holder Rebecca Soni usually dominates, but she's taking the year off.
Also, Marco Koch of Germany qualified first in the men's 200 breast in 2:09.39 and China led the women's 4x200 free relay in 7:52.50, with Australia second and the United States third.
Later on Day 5 of 8 in the pool, finals were scheduled in the men's 200 individual medley and 100 free and the women's 200 butterfly, 50 back and 4x200 free relay. The highlight should be the duel between Olympic champion Nathan Adrian and James "The Missile" Magnussen in the 100 free.
Franklin will swim twice later, in the 100 free semifinals and the relay.
For the 100, she has relatively modest goals.
"If I can make the podium, I will be over the moon happy," said Franklin, who was fifth in London. "I'd be really, really happy with a 52. If it puts me on the podium, that's awesome. If it doesn't, that's fine too."
Campbell, meanwhile, is going for gold. Her astonishing 52.33 in the opening leg of the 4x100 relay on opening night of the pool competition was the fastest time ever swum in a textile suit.
The only woman to swim faster was Steffen, whose times came at the peak of the rubberized super-suit era.
"The relay gave me a lot of confidence," Campbell said. "But this is a different race."
Campbell's younger sister, Bronte, swam one heat earlier and advanced to the semifinals in 12th.
Campbell said that watching her sister allowed her to get rid of some nervousness.
"I always get more nervous watching my sister race," she said.
Campbell is doing her best to remain calm and stay healthy after illness ruled her out of the 100 free at last year's London Games.
"I literally watched an entire year's work get flushed down the toilet," she said.