Mollie O'Callaghan has put the disappointment of losing her 200m world record behind her to storm to victory in a stacked women's 100m freestyle at the Australian Swimming Trials in Brisbane.

World champion O'Callaghan edged out Shayna Jack in a thrilling race that had a packed Brisbane Aquatic Centre roaring in delight.

Jack, who was in tears before even leaving the pool, got a huge ovation from the crowd after she made an individual spot at the Olympic Games for the first time.

"I've said to myself, 'I have nothing to prove, I've come back and I think that tells enough'," a tearful Jack said.

"But I just always thought of this moment and how do I get to this moment, and how do I make it come true?

"It's one of those things that every little girl dreams of, and I've always dreamt of representing my country at the Olympics.

Jack, who spent time out of the pool dealing with a ban for an adverse finding in an out-of-competition drug test in 2019, said she used people's doubts as motivation. 

"I think, for me, it's just using every bit of motivation from anybody who ever doubted me and knowing that I reached points of absolute despair and not even knowing if I wanted to return to the sport.

"It's just happiness. I'm just so proud of myself and I couldn't have done it without so many people. 

"It's pride for myself and pride that I get to prove to everybody that I deserve to be here. And this is what I was born for."

Meg Harris finished in third spot, with Bronte Campbell fourth.

"Personally I'm a bit disappointed," Harris said.

"But I mean, that's just the sport. I wasn't able to back up tonight and the girls were and they deserve this."

O'Callaghan, who was beaten in the 200m freestyle by club mate Ariarne Titmus on night three, said she learned a lot about herself over the last 24 hours.

"It's crazy if you're not upset about the 200 or anything," O'Callaghan said.

"I should be really proud of myself. I'm only 20. I've had maybe three years of experience in the senior team.

"I got to learn so much about myself and nerves and that I can swim regardless of being up at night crying before the race or throughout the day, just being so tense and so wound up because I've never had to deal with the pressure of being a world record holder before nationals.

"I just got to swim and have fun and then this is the pinnacle for our sport, Olympic year, we built up for this. 

"It's a big learning curve for me."

Fresh faces brighten up Paralympic team headed for Paris

Meanwhile Brenden Hall was confirmed to be heading to his fifth Paralympic Games and Alexa Leary her first when Australia's swim team for Paris was named after competition on Friday night.

Thirty swimmers were named to the team, including Tokyo sprint king Rowan Crothers, three-time gold medallist Lakeisha Patterson, 15-year-old Holly Warn and 35-year-old Grant 'Scooter' Patterson.

Team Australia won 33 medals at the Tokyo Paralympics, including eight gold, but this squad represents somewhat of a changing of the guard.

"It's really exciting to see a bunch of rookies on the team this year, it's really exciting to see what we can do," Hall told Channel Nine.

Greg Towle will coach the squad to the Paralympics, which begin on August 28.

Stubblety-Cook claims spot in the 200 back

Elsewhere, defending Olympic champion Zac Stubblety-Cook booked his spot at the Games in the 200m breaststroke.

Pushed all the way by Joshua Yong, Stubblety-Cook overcame a sluggish start to swim 2:07.40 and punch his ticket to Paris.

"I'm just still looking for my best race," Stubblety-Cook said.

"I've not done a PB in two years, so I'd like to have my best race in Paris and that's all I can do.

"I've been trying to work on it [my start] for years, so I'm kind of used to coming up and Young's got a good start.

"I've always raced like that, I like pull it out and all I'm thinking is, don't panic, you're OK, you can swim."

Australia's only male individual swimming gold medallist at the Tokyo Games finished third in Monday's 100m breaststroke final behind Sam Williamson and Yong, who will now swim in two events in Paris. 

"If you told me that this would happen, I would not believe you," Yong said.

"I'm just very excited to be able to say I booked two spots."

In the women's 200m breaststroke, Ella Ramsay won a spot at a second event in Paris with a stunning late surge to pull away from Jenna Strauch, who faded to finish just 0.13 seconds outside the qualification time.

"It wasn't my number one priority at all," 19-year-old Ramsay said, with her main focus Saturday's 400 IM on her mind.

"But to just qualify two other events leading into that, I was just proud of myself and took the pressure off.

"I'm happily surprised. I knew I put in the hard work. I've been training the best I ever have, it's just about controlling my nerves, the pressure around me and just putting that swim together nicely."

The result was tough to take for those who did not make the squad, with 2021 Olympian Abbey Harkin left distraught in the warm-down area.

ABC Sport will be live blogging every day of the Paris Olympics from July 27 (Australian time).

The 'massive risk' for sickly Sam Short

In the 1,500m, heavy favourite Sam Short withdrew on account of a lingering stomach bug that saw him lose four kilograms in the space of 48 hours three weeks ago.

Coach Damien Jones acknowledged it was a "massive risk" not to swim, knowing that if any of those racing made the qualification time it would risk his spot in the event in Paris.

But, given he had already qualified in the 400m and finished second in the 800m despite battling illness, Jones thought it was an acceptable risk.

"I've got to look at his health," Jones said.

"And swimming tonight? How detrimental is that going to be to his preparation in six weeks time in Paris?"

Despite suffering from the debilitating effects of the stomach bug that, had the trials been even a week ago, would have ruled him out entirely, Jones has been impressed with the 20-year-old's resilience.

"If there was one person that I needed to swim for my life no matter what, it would be him, because he just loves hurting himself and absolutely will do anything," Jones said.

"And you can see that now, even though that he's not not 100 per cent, he is putting himself in positions to win, he just hasn't been able to finish it off because of the the health. 

Short has twice swum the qualification time since March 1 2023, the start of the qualification window.

Having already earned his spot in the team for Paris in the 400m freestyle, selectors can make include him in the 1,500m despite not swimming in Brisbane after no other swimmers made the cut on Friday.

In the men's 200m back, both Bradley Woodward and a fast-finishing Se-Bom Lee crashed under the qualification time to head to Paris.

Woodward, who missed out on the team three years ago, was thrilled to finish on top of a quality field.