Brisbane - Kyle Chalmers beat Clyde Lewis by a fingertip on Monday to clinch a spot in the 200 metres freestyle at next month's world championships, as Mitch Larkin narrowly missed a new Commonwealth record in the 100m backstroke.
Rio Olympic 100m champion Chalmers, who is the current 200m Commonwealth gold medallist, surged over the final 25m to touch in one minute 45.76 seconds at the Australian trials.
Lewis came second to deny Cameron McEvoy, Mack Horton and Thomas Fraser-Holmes a place on the team over the distance.
"I actually swim most of my race with my eyes closed but I had a look in the last 25 and put my head down," said Chalmers, whose main event is the 100m.
"I'm putting as much focus on the 200 as the 100. Doing the 200 is good for my fitness," he added.
Larkin, the 2015 world champion, stormed home in 52.38 seconds, fractionally outside his own Commonwealth record, to ensure he will be in South Korea as he looks to reclaim his title from China's Xu Jiayu.
The world record sits at 51.85, set by American Ryan Murphy in 2016.
Only two spots for the championships are available in each individual event being contested over six days in Brisbane, with no one else setting a fast enough time to join Larkin.
Teenagers Minna Atherton and Kaylee McKeown upset veteran Emily Seebohm in the 100m backstroke to book their seats on the plane.
Atherton, 19, clocked a personal best of 59.20, the third fastest time ever by an Australian, to narrowly beat 17-year-old McKeown, who backed up from a sizzling performance on Sunday when she won the 200m individual medley.
"I'm really excited by my time tonight, really happy to do that," said Atherton.
Seebohm, the reigning 200m backstroke world champion, still has a chance to make her seventh world championships when she swims her favoured event later this week.
Jess Hansen was fastest in the women's 100m breaststroke, but her 1:07.06 was outside the world championship qualifying time.