Chalmers on Tuesday night secured a shot at becoming the first Australian man to win consecutive Olympic gold medals in the blue riband event.

The reigning champ triumphed at Australia's Olympic selection trials in a swift 47.59 seconds - just 0.01s slower than his golden swim at the 2016 Rio Games.

And Chalmers is challenging his rivals including American Caleb Dressel, Great Britain's Duncan Scott and Russian Kliment Kolesnikov to turn up the heat under the Olympic spotlight in Tokyo.

"That is what excites me most, I want to be a part of one of the greatest races in history," Chalmers said.

"I know there's a lot of guys that are swimming fast at the moment - obviously it's a bit easier to swim fast at trials and what-not.

"You have got to do it when the pressure is on and when it counts the most.

"So it will be interesting to see how quickly we can go in five weeks' time."

The 22-year-old warned his rivals he was a much-improved swimmer from the raw brute who triumphed in 2016.

"My skills have come a long way, especially from Rio to now, but they're still progressing as the season goes on," he said, forecasting further technical gains at a pre-Games camp in Townsville.

"I am lucky to have my skills coach coming away with me to Townsville so I will do 10 days of intensive skills while I am up there.

"And then it's all up to me to do one good turn and one good dive when it counts."

Earlier, Zac Stubblety-Cook set a 200m breaststroke Commonwealth record as his rival Matt Wilson's Olympic heartbreak continued.

Second-placed Wilson finished 0.24 seconds outside the qualifying time specified by Swimming Australia.

Wilson's dejection mirrors 2016 when he won at trials but was 0.26s shy of the qualifying mark to miss the Rio team.

"It's pretty gut-wrenching seeing that," Stubblety-Cook said of his rival.

"It's just the nature of the sport. It's tough, there's no other word for it."

Wilson also lost his Commonwealth record to Stubblety-Cook, whose time of two minutes 06.28 seconds was the second-fastest ever and just 0.16s off the world record of Russian Anton Chupkov.

In the women's 200m butterfly, victor Brianna Throssell booked her berth on the Tokyo team, as did Madeleine Gough and Kiah Melverton in the new Olympic event, the women's 1500m freestyle.

Australian Associated Press