Already with a relay gold and butterfly bronze, Australia's versatile McKeon emphatically led allcomers through Wednesday night's 100m freestyle heats.

McKeon clocked 52.13 seconds, some 0.06 seconds inside her previous personal best set six weeks ago at Australia's selection trials.

Australia's opening ceremony joint flagbearer Cate Campbell was fourth-fastest into Thursday's semi-finals in 52.80.

Hong Kong's Siobhan Haughey (52.70) was second through the heats followed by Great Britain's Anna Hopkin (52.75).

McKeon and Campbell were part of victorious Australia's 4x100m freestyle relay team on Sunday.

And McKeon also has pocketed a bronze in the 100m butterfly in a program that could reap seven medals.

McKeon is also among the favourites for the 50m freestyle and could swim in three relays including Thursday's women's 4x200m freestyle final.

The women's relayers - Mollie O'Callaghan, Meg Harris, Briana Throssell and Tamsin Cook - easily won their heat and were fastest qualifiers for the final.

The Australians clocked seven minutes 44.61 seconds, some three seconds ahead of the United States, and have big guns Emma McKeon and Ariarne Titmus to swim the final.

In the men's 200m individual medley heats, medal hopeful Mitch Larkin was ninth fastest into the semi-finals.

Jenna Staunch advanced in the women's 200m breaststroke as ninth-quickest but compatriot Abbey Harkin was 17th, one shy of a semi-final berth.

And in the men's 200m backstroke, Tristan Howard booked a semi-final berth when 10th fastest in the heats.

Australian Associated Press