To watch Kaylee McKeown swim backstroke is to witness near perfection in the water.

The Griffith University swimmer conveys the kind of graceful elegance that utterly belies her incredible speed.

Having already qualified for the Games in the 200m medley, McKeown could now focus on her more favoured backstroke events.

That started with the 100m on night two of the Australia Olympic Trials at the Brisbane Aquatic Centre, and the 22-year-old booked her spot in a second individual event with victory in 57.41 — the second fastest time in history — just ahead of freestyle sensation Mollie O'Callaghan.

Despite claiming victory, McKeown, who owns all the world records in the backstroke from 50m to 200m, had to work for her win, pushed all the way by O'Callaghan, who also qualified in a stunning time of 57.88.

"I'm a little bit disappointed [with the time]," McKeown said after the race.

"But, I've booked myself another ticket for Paris and that's just another chance to go faster." 

McKeown admitted fatigue from Monday's Commonwealth Record in the 200m IM clearly played a part in a time that may have been below her expectations, but still surpassed anything her rivals have shown themselves capable of.

The four-time World and three-time Olympic champion knows to expect the same in Paris. 

"The Olympics is just like that," she said.

"If all goes to plan I'm going to have nine individual events, plus relays, so I have to put myself in harms way here."

The terrifying thing is, she often looks like she's taking it easy.

Her heat swim, as was the case in Monday's 200m medley, was second fastest, but was swum with the ease of someone chilling in their family pool on a lazy summer's day.

She did have to work harder in the night session though, pushed by 200m freestyle world record holder O'Callaghan.

Aged 20, O'Callaghan already has three Olympic medals — two of them gold — and eight World Championship medals.

All of those senior international medals — 30 in all — have come swimming freestyle, but as is the case with many crawl exponents the backstroke plays a major role in her training.

And she's clearly quick too. Very quick.

"I'm happy with anything to be honest," O'Callaghan said of her swim.

"It's 100 back, it's a fun event, I don't really train for it, so to go out there and do a 57 is just amazing.

"I put a lot of pressure on myself regardless whether it's a main event or not, so I'm really happy with the outcome."

O'Callaghan is not sure yet whether she will even swim this event in Paris, despite the impressive showing.

"It really depends if I qualify for the next two events [the 200m and 100m freestyle]," O'Callaghan said of the prospect.

Only four women had ever swum 58.00 or under for 100m long course backstroke: McKeown, Americans Regan Smith and Kathleen Baker, and Canadian Kylie Masse. 

Now O'Callaghan has too.

Unfortunately, four-time Olympian Emily Seebohm was unable to complete a fairytale comeback.

The 32-year-old launched her extraordinary attempt at making a fifth Games just eight months after becoming a mother for the first time.

After scraping into the final as eighth-fastest qualifier, Seebohm finished seventh in the final.

"I'm older and that speed isn't as quick as what it used to be," Seebohm said after her heat swim.

"I think the 200m will be a little bit better for me."

Seebohm could still become the first swimmer to compete at a Games as a mother since Hayley Lewis — who was in the stands watching son Kai Taylor swim — in 2000 and would have been just the third all-time.

Mitch Larkin admits the curtain is coming down

At the same end of the spectrum to Seebohm is Mitch Larkin.

The three-time Olympian is chasing one last shot at the big time before hanging up his competition togs at the end of the year.

His heat swim of 54.76 in the 100m backstroke — the fourth-fastest qualifying time — was the fastest he's been since undergoing surgery for a 4cm tear in his shoulder.

"I think that's the metric I try to judge everything off now," Larkin said following his heat swim.

"I've struggled since surgery getting that easy speed, that simple, raw power," the 2016 Olympic 200m backstroke silver medallist added.

"For the last three months I've really tried to chase that, that easy speed. My back end is pretty good but you obviously need those top end gears to come home strong as well."

Larkin could have cause to be frustrated. Angry, even, at the way his body let him down during his preparation for the 2022 Commonwealth Games and World Championships.

But that's not how Larkin operates.

The affable, engaging Queenslander accepts whatever has been thrown at him with incredible grace and humility, driven by a desire not to waste a single minute and his love for the sport.

"My surgeon said, 'look, realistically you may never swim again or you may never swim at the top level again,'" he says.