And Jack will be joined on the Dolphins team by pop star Cody Simpson, who has earnt Commonwealth Games selection and a likely swim at the world titles in the 100 metres butterfly.

Jack finished second behind Mollie O'Callaghan in the 100 metres freestyle final at the national championships on Wednesday night in Adelaide.

Jack's swim earns her automatic selection in the event at the world titles in Budapest in June and the Commonwealth Games in Birmingham in July-August.

"Tears of joy," an emotional Jack said.

"I am just overwhelmed with emotions to be back on the team.

"I have made my point and will continue to be fighting back and doing what I do best all the way through to Paris," she said, referring to the 2024 Paris Olympics.

Jack's feat came moments after musician Simpson finished third in the men's 100m 'fly final.

Swimmers finishing in the top two in a final at the nationals secure selection for the world championships in Budapest in June.

And those placing in the top three earn a spot for the Commonwealth Games starting on July 28 in Birmingham.

Simpson finished behind winner Matt Temple and Kyle Chalmers in his 'fly final.

But Chalmers will skip the worlds to focus on the Commonwealth Games, meaning Simpson is a likely discretionary selection for Budapest and a certainty for the Commonwealth Games.

"Wow, it feels really good," Simpson said.

"I certainly didn't even expect it to even be a possibility until 2024 so that stuff has started to happen so quickly is unreal."

Australian Associated Press