Shayna Jack is on track to return to the Australian swim team while pop star Cody Simpson has hit a fresh high at the national championships.
Jack, on the comeback trail after serving a doping ban, won her 100 metres freestyle heat on Wednesday's opening day at the nationals in Adelaide.
And Simpson, the global pop star who has returned to the pool, set a personal best in the 100m butterfly.
Simpson clocked 51.79 seconds in his heat, bettering his previous benchmark of 52.66 set in April.
He was second-fastest into Wednesday night's final behind national record-holder Matt Temple (51.64) with Kyle Chalmers (52.10) third-quickest.
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.
Jack (53.27) was equal second-quickest into Wednesday night's 100m freestyle final, clocking the same time as Meg Harris, with Mollie O'Callaghan (52.83) the pacesetter.
Jack was initially banned for four years after testing positive to the banned substance Ligandrol about three weeks before the 2019 world championships.
The Queenslander appealed her ban to the Court of Arbitration for Sport which reduced her suspension to two years, finding Jack did not knowingly ingest the substance.
Jack's automatic selection for an individual 100m freestyle swim at the looming worlds and Commonwealth Games is complicated by the absence of Olympic champion Emma McKeon from the nationals.
McKeon's gold medal in the event at last year's Tokyo Olympics gives her automatic selection but she will miss the world titles to focus on the Commonwealth Games.
That means Jack needs to finish in the top two in Wednesday night's final to be assured of returning to the Dolphins team in an individual event.
Other Wednesday morning heats at the nationals included Elijah Winnington being quickest in the men's 400m freestyle followed by Sam Short and 2016 Olympic gold medallist Mack Horton.
Jenna Strauch and Abbey Harkin topped qualifying for the women's 100m breaststroke and Brad Woodward was fastest in the men's 200m backstroke heats.
