William Yang is the new Australian men's 100 metres freestyle champion.

The 23-year-old won the title at the Australian Swimming Championships in Adelaide in a personal best time of 48.55 seconds, with two-time Tokyo Olympics relay bronze medallist Zac Incerti (48.65) second and 16-year-old sensation Flynn Southam (48.76) third.

Australia's sprint king Kyle Chalmers was not competing in the race after he elected to only race butterfly events at the championships.

It is the first time in years that the Olympic 100m freestyle gold and silver medallist has not competed in the national championships.

"It's a little weird when you don't have the big fella (Chalmers) pacing up and down and talking a bit of smack to you," Incerti said.

Yang and Incerti will swim in the individual 100m freestyle races at the world championships next month in Budapest and at the Birmingham Commonwealth Games in July.

Yang said he recently took eight months off from the sport and was close to quitting.

"In the past I had too many thoughts in my brain," said Yang, who is a former backstroker.

"It's not just swimming, it was like financially, peer pressure. I think it's a bit different coming from an Asian background as well. You have family expectations."

Asked to describe his family expectations, Yang said :"I can't really describe it, I can just feel it.

"I don't think my family actually put that much expectation on me, but I felt it."

But Yang said both his parents, who were born in China, would be proud of him.

Incerti, who has spoken openly about his mental health struggles in the past, said sport was going in the right direction in terms of talking about depression and anxiety.

"I've had some of my darkest times with mental health and whatnot," he said.

"I just try to help as many people as I can and show people that it does always get better even though it might not feel like it at the time."

Yang and Incerti both spoke glowingly about Southam, who is set to be selected for the world championships and Commonwealth Games in the 4x100m and 4x200m freestyle relay teams.

"He's [Southam] going to do amazing things in the future, and I can't wait to be next to him and maybe get beaten by him one day," Incerti said.

"That guy's [Southam] going to be real, real good," said Yang.

Southam described the experience of competing in the 100m freestyle final as "awesome"

"I've learnt so much from those guys, seeing how they go about their business in the marshalling room," he said.

"It's awesome to swim alongside them, it's a privilege and I really just have a lot of respect for those guys.

"It was just a great experience being here at my first trial meet only being 16. I'm just really privileged to be here."

Southam has been compared to both Chalmers and Ian Thorpe because he has swum similar times to what those two were swimming at the same age.

"I respect Kyle, I respect Thorpie, those guys are legends of the sport," Southam said.

"But I know Kyle had his own path, Thorpie had his own path … individual world champion at 15. It's ridiculous, I'm a big fan of his.

In other events, three-time Olympic gold medallist Kaylee McKeown won the women's 200m backstroke final.

McKeown won in a time of 2:05.31, more than a second outside her Australian record.

Mollie O'Callaghan (2:08.48) finished second and Minna Atherton (2:10.20) was third.

McKeown and O'Callaghan will represent Australia at the world championships and Commonwealth Games.

O'Callaghan said she planned to swim the 100m and 200m freestyle races at the two competitions, in addition to the 100m backstroke and the relays.

Gough punches his ticket for Budapest

Bowen Gough defended his title in the final of the men's 200m butterfly in a time of 1:56.49.

Gough will be the only Australian to swim the event in Budapest and Birmingham. It the first time the 24-year-old has made an Australian team.

Olympic bronze medallist Brendon Smith defended his national title in the men's 400m individual medley.

Smith (4:11.88) will be joined by Se-Bom Lee (4:14.77), who finished just .01 ahead of third-placed Kieren Pollard (4:14.78).

"It's a pretty stacked field … so you can't get complacent, as soon as you do that you get beaten," Smith said.

Nineteen-year-old Lani Pallister capped her win in the women's 800m freestyle by claiming the 1,500m freestyle in a personal best time of 15:55.40.

"I'm really excited. I think the journey has been a lot more special than the meet itself," Pallister said.

Moesha Johnson, who came second behind Pallister, will swim the event at the world titles, along with the 5km and 10km open water races.