McKeown survives scare to book world championship ticket

World record holder Kaylee McKeown survived a huge fright before winning the 50m backstroke at the Australian world championship trials on Monday after being disqualified from her heat and then reinstated.

The reigning Olympic 100m and 200m backstroke gold medallist hit the wall in 27.33 seconds to edge Mollie O'Callaghan (27.39) in the final and book her ticket to the championships in Singapore next month.

It came after a nerve-racking day for the 23-year-old, who won her morning heat convincingly but was disqualified over a slight head movement on the blocks, where competitors must be absolutely still.

The distraught gold medal favourite and 2023 world champion appealed against the disqualification and had to endure an anxious two-hour wait before being reinstated.

"I guess it's just the way that the cookie crumbles," said McKeown. "But you know, I'm really happy to have had the chance to race tonight.

"It wasn't exactly what I wanted or what I've trained for, but I'm on the team, so I'm happy for that."

Reigning world champion Isaac Cooper was fastest in the men's 50m race, touching in 24.69 to qualify.

McKeown, who swept the 50-100-200 backstroke treble at the 2023 worlds, will also race over 100m and 200m at the trials in Adelaide.

However, she has dropped the 200m medley despite winning bronze at the Paris Olympics.

That opened the door to 20-year-old Ella Ramsey, who made the Olympic final last year but was forced to withdraw with Covid.

Ramsey clocked 2:09.21 to be well under the qualifying time, with Tara Kinder also making the grade.

The trials represent a changing of the guard for Australia, with several big-name swimmers either retiring or taking a break.

Australia's most successful Olympian Emma McKeon hung up her goggles after Paris, as did other stalwarts including Mitch Larkin, Brianna Throssell and Jenna Strauch.

Four-time Olympic gold medallist Ariarne Titmus -- who lost her 400m freestyle world record to Canadian Summer McIntosh at the weekend -- is on an extended break.

In Titmus's absence, Lani Pallister will lead Australia's charge in Singapore against McIntosh after dipping under four minutes for the first time, touching in 3:59.72.

"It's been on my mind all year," Pallister said of breaking the barrier to join an elite group.

She is a medal chance in Singapore but still a long way behind McIntosh, whose new world record was a sizzling 3:54.18.

Sam Short, the 2023 world champion, stormed to the men's 400m title in 3:41.03 ahead of Elijah Winnington (3:43.99), who took silver in Paris behind German world record holder Lukas Maertens.

"I've worked really hard, I booked my ticket and keen to race the best in the world," said Short.

With the 100m butterfly missing McKeon, Alexandria Perkins impressively stepped into the void, posting 56.42 ahead of Lily Price with both making the plane to Singapore.