It's no secret that Australian women's swimming has extraordinary depth.

But the women's 200m free takes things to a whole new level.

The event is one of the most hotly contested events at this Australian Trials as Australia's best fight it out to not only make one of two individual spots, but earn a place in a relay team that should challenge for gold in Paris.

Headlined by world record holder Mollie O'Callaghan and defending Olympic champion Ariarne Titmus, the depth of the field is simply extraordinary.

"Our women's 200m is absolutely stacked," Shayna Jack, who qualified sixth-fastest said.

"We've got so many amazing women in this event, we all know how much of a privilege it is to represent Australia in the 200 and also the 4x200, because we do have that world record.

"This morning everyone's just got to go for it."

All four of the women that set the 4x200m freestyle relay world record of 7:37.50 at the 2023 World Championships: O'Callaghan, Jack, Titmus and Brianna Throssell were in action — and all made the final.

Lani Pallister, who swam in the heats ahead of that world record swim also booked her place in the final, although fellow heat swimmer Kiah Melverton was only fast enough for 12th.

"I have been a heat swimmer two World Champs in a row, and it sucks," Pallister, who qualified third-fastest, said after her heat swim on Wednesday morning.

"I understand the importance in playing a part and that sort of thing but I think there's a huge difference in having the opportunity to stand up in a final.

"It's one of Australia's most important events and I think it's an event that we have the opportunity to do really well in."