Ryan Napoleon and Kylie Palmer won their 400-metre freestyle events to claim the first tickets to July's Shanghai world championships at the Australian trials in Sydney on Friday.
Napoleon clocked three minutes 45.16 seconds and bettered his personal best set during the supersuit era to take the men's 400m freestyle final.
Thomas Fraser-Holmes (3:46.54) claimed second to also book a spot on the team.
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Palmer (4:04.29) also set a personal best and clocked the second fastest time in the world this year to take the women's 400m freestyle, with Bronte Barratt (4:04.36) taking the second spot on offer.
Five-time Commonwealth Games gold medallist Alicia Coutts was impressive in qualifying fastest for both the 100m butterfly and 200 individual medley finals and a likely showdown with the returning Stephanie Rice.
Coutts, 23, topped a hot field ahead of Saturday's 100m butterfly final, clocking 58.32secs, the fifth fastest time in the world this year.
She backed up less than half an hour later to top the semi-finals for the 200m individual medley, easing off significantly in the final lap to post 2:13.35, with Rice (2:13.90) in equal third.
Triple Beijing Olympic champion Rice was absent at last October's Delhi Games following shoulder surgery.
Rice said it would be "tough" to beat Coutts.
"She's swimming well, I always knew that she would swim well and when you come off a high you always have that extra adrenaline," Rice said.
"I think I'm out of racing practice, I would have like to have a few more races under my belt."
The Australian championships continue until April 8.
