There hadn't been a world record set at U.S. Swimming Trials since 2008. Four nights into the week in Indy, the Lucas Oil Stadium crowd has already been treated to two such performances at the 2024 U.S. Olympic Swimming Team Trials presented by Lilly.

The latest came on Night 4 when backstroke ace Regan Smith wrote herself back into the record books in the women's 100m backstroke, the same event in which she originally set the record in 2019 (before it was overtaken in 2023). 

Tuesday night also saw Bobby Finke demonstrate his distance dominance, as well as the evening session debuts for Caeleb Dressel and Kate Douglass as both look to affirm their spots at top stars on Team USA.

See below for event-by-event recaps, highlights and results from Indy.

Men's 100m freestyle semifinals

In the second showdown of the day between Caeleb Dressel and Jack Alexy in the 100m free, Alexy backed up his win in the prelims with another top finish in the second semifinal.

Alexy touched in 47.33 seconds, after turning at the 50-meter mark under world-record pace. Dressel, the defending Olympic gold medalist, finished two tenths behind in second.

However, it was 20-year-old Notre Dame Fighting Irish swimmer Chris Guiliano who claimed the top seed for the final, winning the first semifinal in 47.25 seconds.

As many as six of the eight finalists could find themselves on the Olympic team as the U.S. men's 4x100m freestyle relay team takes shape.

1) Chris Guiliano | 47.25
2) Jack Alexy | 47.33
3) Caeleb Dressel | 47.53
4) Hunter Armstrong | 47.59
5) Destin Lasco | 47.90
6) Macguire McDuff | 48.04
7) Ryan Held | 48.05
8) Matt King | 48.11

Men's 200m butterfly semifinals

Carson Foster, one of the incoming favorites in this event, scratched ahead of the prelims earlier in the day opening things up for the rest of the field.

Luca Urlando, who has battled injuries throughout an otherwise promising young career, earned the top time of the session, winning the first semifinal in 1:54.64.

Semifinal No. 2 winner, Thomas Heilman, snagged the other middle lane for the final, which could go any number of ways.

1) Luca Urlando | 1:54.64
2) Thomas Heilman | 1:54.93
3) Mason Laur | 1:55.05
4) Dare Rose | 1:55.25
5) Jack Dahlgren | 1:55.65
6) Colby Mefford | 1:55.72
7) Zach Harting | 1:56.52
8) Trenton Julian | 1:56.73

Women's 100m backstroke final

The 100m backstroke world record is Regan Smith's once again.

The American star, who originally set the record in 2019 before it was eclipsed by Australia's Kaylee McKeown in 2023, won the final in 57.13 seconds. She lowered the all-time mark by a full two tenths of a second.

"I am so proud of myself," Smith told NBC's Melissa Stark after the race. "Backstroke is hard for me sometimes, but to fight back like this and get [the record] back means a lot."

Smith now heads to Paris and a showdown with McKeown, which surely will be one of the most anticipated events of the Olympic swimming program.

Katharine Berkoff finished behind Smith in second to claim what is likely to be her first Olympic team spot.

1) *Regan Smith | 57.13 (WR)
2) **Katharine Berkoff | 57.91
3) Kennedy Noble | 58.81
4) Josephine Fuller | 59.03
5) Rhyan White | 59.07
6) Phoebe Bacon | 59.37
7) Leah Shackley | 59.40
8) Claire Curzan | 59.57
*Olympic place guaranteed
**Olympic place likely

Men's 800m freestyle final

To nobody's surprise, Tokyo gold medalist Bobby Finke made official his opportunity to defend his 800m free Olympic title in Paris. 

Finke finished in 7:44.22, over five seconds ahead of anyone except fellow Florida Gator Luke Whitlock, who hung with Finke and touched less than a second behind to, in all likelihood, lock up a spot next to Finke on the Olympic team.

Finke, who said he started feeling the "hurt" of distance racing even before the halfway point of the race, posted a time five seconds slower than the American record he set at the 2023 World Championships.

1) *Bobby Finke | 7:44.22
2) **Luke Whitlock | 7:45.19
3) Daniel Matheson | 7:49.34
4) David Johnston | 7:50.23
5) Ross Dant | 7:54.56
6) Charlie Clark | 7:57.28
7) Will Gallant | 7:58.22
8) Sean Green | 7:59.01
*Olympic place guaranteed
**Olympic place likely

Women's 100m freestyle semifinals

A star-studded final is shaping up in one of the most exciting events in the pool featuring two four-time world champions (Torri Huske and Kate Douglass), two 2016 Olympic gold medalist (Simone Manuel and Abbey Weitzeil) and a newly-crowned word-record holder (Gretchen Walsh).

Huske set the top pace in the semifinals, but any two of those women could emerge as the duo to represent the U.S. in the event.

Luckily, all five (plus one other) have an opportunity to comprise a stacked U.S. 4x100m freestyle relay team, which will also take shape in the final.

1) Torri Huske | 52.90
2) Simone Manuel | 53.16
3) Kate Douglass | 53.21
4) Gretchen Walsh | 53.33
5) Abbey Weitzeil | 53.66
6) Beata Nelson | 53.92
7) Catie Deloof | 53.98
8) *Erika Connolly | 54.09
8) *Anna Moesch | 54.09
*Advance to swim-off

Men's 200m breaststroke semifinals

Nobody was more surprised with Matt Fallon's sub-2:08 time than Matt Fallon himself. The University of Pennsylvania swimmer even flirted with Josh Prenot's American record, touching just less than three tenths shy of the mark.

Josh Matheny won the first semifinal in 2:08.79, good enough for the No. 3 seed in the final.

Nic Fink, who already qualified for Paris in the 100m breaststroke, earned himself a lane for the final as well.

1) Matt Fallon | 2:07.39
2) A.J. Pouch | 2:08.00
3) Josh Matheny | 2:08.79
4) Jake Foster | 2:09.57
5) Daniel Roy | 2:09.65
6) Nic Fink | 2:09.80
7) Josh Bey | 2:11.09
8) Will Licon | 2:11.14