Irvine, California: From an Australian trying to end one of swimming’s most extraordinary winning streaks to a first glimpse at some of the rivalries that could define the 2028 Los Angeles Olympics, the Pan Pacific Championships in Irvine this week are about more than just medals.

These are the five races and storylines to watch ahead of racing on Wednesday (Thursday AEST) between the best of Australia, USA and other non-European nations. Heats begin at 3am Thursday AEST, with finals from midday AEST each day on Channel 9 across four days of high-quality racing.

Women’s 800m freestyle

Lani Pallister’s showdown with arguably the greatest female swimmer in history, Katie Ledecky, in the women’s 800m freestyle on Saturday (Sunday, AEST) is not to be missed.

Since winning her first Olympic gold at London 2012 as a 15-year-old, Ledecky has never lost an 800m freestyle final at a major international meeting. In fact, since she was 13 in 2010, the only 800m final Ledecky has lost was to Summer McIntosh at a domestic meeting in 2024.

Unfortunately, McIntosh won’t contest the 800m here because it clashes with the 200m individual medley.

The trio produced one of swimming’s great races at last year’s world championships, when Ledecky (8:05.62) narrowly edged Pallister (8:05.98) and McIntosh (8:07.29).

It was a coming-of-age performance for Pallister, who arrives in Irvine in terrific form after winning three individual gold medals at the Commonwealth Games.

Pallister is now trained by Dean Boxall, who helped Ariarne Titmus take down Ledecky in the 400m freestyle and become the dominant force in the event from 2019 to 2024.

Their times this year suggest another thriller is looming. Ledecky has clocked 8:10.16 (January), 8:08.57 (March), 8:12.68 (May) and 8:12.87 (June). Pallister, by comparison, has gone 8:11.28 (April), 8:13.41 (June) and 8:11.12 (July).

This is already being billed as one of the races of the 2028 Los Angeles Olympics, where Ledecky will attempt to win an unprecedented fifth consecutive 800m freestyle title. Imagine the scenes if Pallister triumphs in front of 40,000 partisan American supporters at SoFi Stadium.

Consider Irvine the entree before the main course.

**Women’s 50m freestyle **

Australia’s Meg Harris has enjoyed an outstanding two years, winning silver at the Paris Olympics, gold at last year’s world championships and six gold medals (four relays) at the recent Commonwealth Games.

But the 24-year-old is set to run into a formidable group of American sprinters in what looms as an excellent gauge of where she sits two years out from LA 2028.

Harris clocked 24.02 to win her maiden individual world title last year but four Americans have since gone faster: world record holder Gretchen Walsh (23.55), Kate Douglass (23.59), Simone Manuel (23.97) and Torri Huske (23.98).

Countries can enter as many swimmers as they like in the heats but only the fastest two from each nation can progress to the final, meaning there will intense competition among the Americans.

Australia, meanwhile, have undergone a significant changing of the guard in the 50m freestyle, with Cate Campbell, Bronte Campbell, Emma McKeon and Shayna Jack all retiring over the past two years. It would be some victory if Harris could pull it off.

The women’s 50m freestyle is on Saturday (Sunday AEST).

**Men’s 800m freestyle **

Sam Short has made no secret of his desire to “smash” American Bobby Finke at these Pan Pacs. He gets his first chance on day one of competition on Wednesday (Thursday AEST).

At Australia’s trials in June, Short became the fastest man in history outside the supersuit era when he clocked 7:36.73 to lower his Australian record.

A similar time in Irvine would put him in a strong position to win, with Finke’s personal best of 7:38.67 coming three years ago at the world championships in Fukuoka, where Short finished one place ahead of him in second.

Short says he has arrived in Irvine fully rested and tapered for the 800m after the Commonwealth Games.

A world record appears unreachable, given China’s Zhang Lin clocked a remarkable 7:32.12 in a supersuit in 2009, but another personal best is firmly on Short’s radar.

Then comes the 1500m freestyle, where Finke is the world record holder and Short is as competitive as they come. Their two distance battles will provide plenty of fireworks.

**Women’s 4x100m freestyle relay **

Few events have been as synonymous with Australian swimming success over the past decade as the women’s 4x100m freestyle relay.

Australia have dominated the event since the 2012 London Olympics, with the notable exceptions of the 2017 and 2024 world championships. Most countries did not send their best teams in 2024, including Australia.

Now that dominance faces a serious test.

Mollie O’Callaghan has opted to skip Pan Pacs because of a back issue, while Shayna Jack retired after the Commonwealth Games, leaving Australia with plenty of work to do against an American squad featuring Simone Manuel, Torri Huske, Kate Douglass and Gretchen Walsh.

American Anna Moesch has also broken 52 seconds twice this year – something O’Callaghan has never managed in her career – but won’t compete at Pan Pacs because the US team was selected last year.

Harris has spoken about the importance of maintaining Australia’s dominance in an event that has become a source of enormous national pride. Australia are the world record holders.

Without O’Callaghan and Jack, Pan Pacs will provide a serious test of Australia’s depth, with Olivia Wunsch and Milla Jansen among those who will need to step up in the final on Friday (Saturday AEST).

Australians against Summer McIntosh

The Canadian superstar and three-time Paris Olympic champion has entered the 200m freestyle, 400m freestyle and both individual medleys (200m and 400m).

McIntosh is heavily favoured to win all four of those events and arrives in Irvine holding four individual world records.

It is a shame McIntosh won’t get to face O’Callaghan in the 200m freestyle, an event the pair are likely to both contest at LA.

Brittany Castelluzzo (2:06.56) and Lizzy Dekkers (2:06.91) won gold and bronze respectively in the 200m butterfly at the Commonwealth Games but McIntosh’s world record of 2:01.65 highlights the enormous gap Australia’s best will be trying to close.

Jenna Forrester is also firmly in the conversation for Olympic medals in the 200m and 400m individual medleys but racing McIntosh is another proposition altogether.

The experience will do Australia’s swimmers the world of good. But after skipping the Commonwealth Games to ensure she was fresh for Irvine, McIntosh is expected to dominate these championships with a handful more world records to celebrate.