The medley relays will unfold in the curtain-closing session of the nine days of racing in the pool at the Paris Olympics, by which time we will know whether Australia is up for winning the women's meet over the United States for a second successive Games after dominance in Tokyo.

All strokes matter, of course, but if the Dolphins are to retain the crown, the filling must stick as close as possible to the significant top-speed advantage of the Americans on breaststroke and butterfly and the bread holding the sandwich together will need to make toast of their opposition with best-ever relay splits on backstroke and freestyle. 

It isn't impossible to imagine the Australians being strong enough for Mollie O'Callaghan or anyone proven or deemed to be better in Paris than the first woman ever to claim 100-200m freestyle World titles, to leave the blocks a second behind do to the Americans what Cate Campbell did to them in Tokyo with a decisive 52.1 gold-grabber on freestyle.

In Paris, the Australians have to be looking at that scenario with cowbells and didgeridoos attached if they're to keep the crown given events at U.S. Trials last month: have World-record swims by Regan Smith on backstroke (57.13) and Gretchen Walsh on butterfly (55.18) hold hands with the top pace of Lilly King on breaststroke and Kate Douglass on freestyle and a perfect day shatters their nation's 2019 world record from Gwangju World titles:

3:50.40 - Regan Smith 57.57wr, Lilly King 1:04.81, Kelsi Dahlia, 56.16, Simone Manuel 51.86

Three years on, Manuel was taking time out, the first three swimmers in the water for the USA and AUS were all but neck and neck and then Abbey Weitzeil swam well in 52.49 but Cate Campbell was in a different, well-practised league apart, on 52.11, the Dolphins taking gold in an Olympic and Oceania record of 3:51.60.