David McKeon and Bronte Barratt were the first swimmers to book places in Australia's team for this year's Barcelona world championships with 400-metre freestyle victories at trials in Adelaide on Friday.
McKeon defended his men's 400m freestyle national title, while Barratt claimed her third women's 400m freestyle crown and first since 2010.
McKeon, 20, clocked the second-fastest time of the year in a personal best of three minutes 43.71 seconds.
His victory followed the disqualification of main rival Thomas Fraser-Holmes, who overbalanced on the blocks ahead of his morning 400m heat and fell into the water.
Barratt, 24, clocked the fastest women's 400m freestyle time of the year in a personal best 4:03.52 to deny second placed Kylie Palmer (4:06.00).
The FINA world championships take place from July 28 to August 4.