Mollie O’Callaghan broke a world record. Kaylee McKeown decided to do the same

Australia’s Olympic swimmers continue to dazzle on the world stage, with Kaylee McKeown breaking the women’s short-course 200-metre backstroke world record a day after teammate Mollie O’Callaghan’s stunning freestyle swim over the same distance.

O’Callaghan shocked the swimming world on Saturday (Sunday AEDT) by obliterating the women’s short-course 200m freestyle record - a performance that came days after Swimming Australia was forced to defend the Olympic champion from false social media posts.

McKeown, meanwhile, rebounded from a shock loss to long-time rival Regan Smith in the 100m backstroke final at the World Cup meet in Westmont, Illinois, which is being held in a 25-metre pool.

Smith had held the 200m backstroke short-course world record since last year in Budapest, with a time of 1:58.04, but McKeown responded on Sunday (Monday AEDT) in emphatic fashion.

The Australian led from the outset before holding off a fast-finishing Smith to win by four one-hundredths of a second in 1:57.87. Smith was also under her previous best.

Lani Pallister also continued her strong form, winning the 1500m freestyle final in 15:13.83. It was the second-fastest time in history behind only American great Katie Ledecky. Pallister finished 0.36 seconds behind Ledecky in the 800m freestyle final (long course) at this year’s world championships in Singapore.

At the same meet, Cate Campbell’s 100m freestyle world record was beaten by the USA’s Kate Douglass.

Campbell’s mark of 50.25 seconds had stood since 2017. Douglass clocked 50.19.

O’Callaghan, the reigning Olympic and world champion in the long-course (50m pool) version of the event, became the first woman to break the one-minute 50-second barrier in a 25-metre pool, clocking 1:49.77.

O’Callaghan also pocketed a US$10,000 bonus ($15,500 AUD) for breaking the world record.

“I was so nervous all day,” O’Callaghan told Swimming World after the race. “I knew I was capable of doing that swim.

“It’s nice to do short course, it’s such a big change from long course. It’s a different beast at the end of the day.

“I have a great support team behind me to get me to this moment.”

O’Callaghan had shown ominous form last week, posting a personal best of 1:50.77.

The record capped a turbulent fortnight for O’Callaghan, who has been the target of a vile fake news campaign on Facebook.

A page with about 13,000 followers has been posting – and continues to do so – fabricated news stories about O’Callaghan, many relating to transgender athlete Lia Thomas.

One post falsely claimed O’Callaghan would boycott the 2028 Los Angeles Olympics if a transgender swimmer were allowed to compete.

Other false posts alleged O’Callaghan had signed a “$13.5 million Netflix deal for a seven-episode documentary”, been “harassed during a promotional event with Emirates”, and been accused by Dutch rival Marrit Steenbergen of using “an illegal performance-enhancing device”. All claims are baseless.

Swimming Australia issued a statement last week condemning the posts.

“There are currently fabricated quotes attributed to Dolphin Mollie O’Callaghan appearing on social media posts,” the statement said.

“At no stage has O’Callaghan been interviewed and provided commentary on transgender athletes. Meta has been advised of the fake news, and O’Callaghan and Swimming Australia have requested the posts to be taken down.”