If 2025 proved anything, it’s that swimming had momentum. In a non-Olympic year, World Records fell in 17 individual events across long course and short course meters. The World Aquatics Championships in Singapore featured some of the most memorable races and storylines in recent memory, while the World Cup in the fall reopened many eyes to what is possible in this sport.

2025 was an incredible year, and here are some of the memorable performances that made it so.

Summer McIntosh Enters the GOAT Conversation

Canada’s Summer McIntosh was destined to be a star when she finished fourth in her Olympic debut as a 14-year-old at the Tokyo Olympics in 2021 in the 400m freestyle. When she won her first Olympic gold medal three years later as a 17-year-old in the 400m IM, she fulfilled the prophecy. With additional Olympic gold in Paris in the 200m butterfly and 200m IM, McIntosh became the 15th swimmer to win three individual gold medals in the same Olympics, and the ninth swimmer to win four individual medals in the same Games.

But what followed was the stuff of legends. Relocating from her training base in Sarasota, Florida, to the south of France with new coach Fred Vergnoux, not only did she not skip a beat, she took a step forward.

At the Canadian Trials in June, McIntosh put on one of the best performances anyone has had in the history of swimming; three world records in five events. It started with a 3:54 in the 400m freestyle, slicing a second off Ariarne Titmus’s mark from 2023 to reclaim the record. Then followed an 8:05 in the 800m freestyle, pushing Katie Ledecky’s 8:04 world mark from earlier in the year the entire way, getting closer than anyone had before.

The next night, she threw down a 2:05 in the 200m IM as she took Katinka Hosszu’s 2015 mark off the books that had seen many challenges over the years but finally succumbed to the Canadian.

The next night, perhaps her best swim of the entire meet, she swam 2:02 in the 200m butterfly to get closer to Liu Zige’s 2:01.81 from 2009 than anyone had ever been before. That record remained so far out there that it was once deemed unbreakable but McIntosh redefined what was thought to be possible in the event. Her swim and the reaction around it, although not a world record, turned heads around the world.

In her final swim of the meet, she took her own 400m IM world record down to 4:23, sitting nearly three seconds ahead of the next fastest performer all-time.

McIntosh became the first swimmer since Michael Phelps in 2008 to set three long course world records in one meet, and the first woman to do so since Inge de Bruijn in 2000.

It was an impressive performance that redefined what many thought was possible in the sport. While the post-Olympic year has been thought of as an “experimental year” McIntosh showed it didn’t have to be that way anymore. She took on a five-event program for the World Championships, an ambitious goal where she didn’t back down one single time. While she didn’t win all five of her individual events in 2025, she set the tone that she wasn’t afraid of anyone. Her World Trials performance kept fans tuning in every single night, while she became a household name in Singapore if she wasn’t already one. In 2025, she put on one of the best performances ever, keeping worldwide interest in a non-Olympic year. 

Katie Ledecky Proves She’s Still the Greatest in Thriller Over Pallister & McIntosh

When Summer McIntosh confirmed she was going to swim the 800m freestyle at the World Aquatics Championships in Singapore, a heavily anticipated showdown with American Katie Ledecky had swimming fans salivating all over the world. Ledecky hadn’t been beaten head to head in a Worlds or Olympics ever - a 12-year winning streak that started back at the 2012 Olympics in London. Her only loss was to McIntosh at a low key meet in Florida in February 2024.

When McIntosh had the meet of her life at the Canadian Trials in June, setting three world records in the 200m and 400m IM and the 400m freestyle, she had the best odds of anyone to take down Ledecky in her best event. Even though Ledecky had broken her own world record in May, McIntosh had all the momentum entering Singapore.

The performance of the United States team in Singapore was clouded by conversations of a bout with acute gastroenteritis, a virus that causes an inflammation of the stomach, that drastically affected the team during training camp. The results were hard to ignore - athletes were scratching out of events at the last minute and some were adding up to three seconds in a 100 meter race. Many of the Americans were struggling to finish races in the final meters, and although gold medals were still being won by individuals, the misses were louder than the successes.

While McIntosh won her first three gold medals with relative ease in the 400m freestyle, 200m IM, and the 200m butterfly, the American fans worried a broken Ledecky streak was imminent.

While McIntosh and Ledecky were the stars of the show, Australia’s Lani Pallister wouldn’t go away either. Pallister had long been deemed a rising star in the world of swimming, dating back to her three individual golds at the 2019 World Juniors. But as she got her senior career underway, illnesses and injuries got in the way. Entering 2025, she was finally healthy and ready to show what she was capable of.

The race lived up in every single way. For 700 meters, McIntosh, Ledecky, and Pallister remained stroke-for-stroke, leaving the crowd waiting with nervous anticipation. Could Ledecky keep her winning streak alive in the clutchest way? Could McIntosh really do the unthinkable and take down perhaps the greatest to ever do it? Could Pallister pull the upset of the century and beat both of them?

As the three flipped at the 750m mark, Ledecky kicked out ahead of her rivals, a signature in her career, and soared to the gold medal. With her final 50m sprint, Ledecky slapped the water in jubilation as the American team’s sigh of relief could be heard from all corners of the world. The tumultuous year that had many looking inward didn’t seem so bad all of a sudden, and the team came together better than ever before to sing the national anthem as one.

McIntosh’s effort, albeit valiant, gave her a bronze medal, while Pallister’s silver and 8:05 capped a career year that had long been in the making.

Leon Marchand Breaks Ryan Lochte’s 200m IM Record

France’s Leon Marchand had a storybook 2024; four Olympic gold medals in his home nation as one of the faces of the Paris Games. He achieved nearly everything he set out to do last year, so what could he possibly do as a follow-up? Without a home Olympics on the horizon, what was keeping him motivated in 2025?

Marchand, who reached sporting celebrity status after Paris with 1.5 million Instagram followers amassed, entered the World Aquatics Championships in Singapore on an abbreviated schedule, dropping the 200m butterfly and 200m breaststroke from his lineup while keeping the 200m and the 400m IM, the events that kickstarted his career back in 2022.

With his first swim at the championships not occurring until day four, Marchand entered the 200m IM semis fresh and ready to drop something big. Although he had already achieved so much, the 1:54.00 world record from Ryan Lochte set in 2011 remained as one of the last accomplishments for the Frenchman.

On the fourth night in Singapore, Marchand unleashed a 1:52.69 in the 200m IM semis to obliterate Lochte’s mark that had stood for so long. While Lochte and his compatriot Michael Phelps dominated the sport for so long, Marchand ended their reign to have his name etched alongside the world record graphics.

It truly was the sign of the end of the Phelps-Lochte era as the rough-and-tough grind-it-out era has slowly given way to a more athletic and agile swimming era where swimming fast at all points of the year is prevalent. Marchand has been one of the faces of this new movement in the sport, and his 200m IM world record was one of the best swims of the entire year.

Hubert Kos Wins World Cup Crown as Bowman Crew Dominates the Pool

Marchand’s relationship with his coach Bob Bowman has been a key part of his legacy as one of the best IM racers of all-time. Bowman, who famously led Michael Phelps to be the greatest swimmer of all-time, etched his own legacy as one of the best coaches of all-time.

When Marchand followed up his world record in the 200m IM with a World title, he was surrounded by two of his training mates, each representing different countries - USA’s Shaine Casas and Hungary’s Hubert Kos.

Kos quietly had a career year in 2025, showcasing his versatility as one of the best swimmers in the world. Kos put up the fastest 200m backstroke in 10 years when he continued his three-year winning streak in the event in Singapore, taking serious aim at Aaron Peirsol’s world record that has stood since 2009.

But what was most impressive was what followed at the World Cup in short course meters. Kos went nine-for-nine in backstroke finals, remaining undefeated across the 50m, 100m, and 200m finals, ending his run in Toronto with world records in both the 100m (48.16) and 200m (1:45.12). For Kos, who started his international career as a 200 IM’er, he showed off the rare mix of speed and endurance to win the World Cup overall crown.

The 200m backstroke world record wasn’t much of a surprise for Kos, who had just missed that the year prior at a home World Short Course Championships, taking a half second off of Mitch Larkin’s 1:45.63 from 2015. It was in the 100m though where Kos really had his moment in the spotlight.

Kos, not one to back down from a challenge, attacked the 100m final race with vigor, and took the world record by surprise, saving his best swim of the three weeks for last. He’s another in the long line of champions coached by Bowman as he’s been a factor in the last couple 100m backstroke major finals, but hadn’t had the speed to match with the best in the world. That swim on the last night of the World Cup showed he’s got the chops and could mean the best is yet to come for him. 

Kate Douglass, Gretchen Walsh Redefine What is Possible

As swimming moves forward into a “swim fast all the time” era, no two swimmers have better embodied that mantra than training mates at the University of Virginia, Kate Douglass and Gretchen Walsh. Their careers have drawn parallels to each other’s - age group phenoms to national junior team members to NCAA champions at the University of Virginia. Now in 2025, they’re two of the best swimmers, not only in the United States, but the entire world, and are two of the faces of a United States women’s team poised for a big showing at a home Olympics in 2028.

Off the backs of nine individual world records at last year’s World Short Course Championships, Walsh became the first woman to swim inside 55 seconds in the 100m butterfly in May, using her powerful dolphin kicks and long arms to take the event into uncharted territory. At the World Championships, Walsh finally broke through for her first individual long course gold in the 100m butterfly, holding off Belgium’s rising star Roos VanOtterdijk, and became the first American woman to win the 50m butterfly World title.

Douglass used her long glide and incredible efficiency in the 200m breaststroke to take down the world record holder Evgeniia Chikunova in the final at the World Championships. Douglass shied away from the 200m IM this year, the event where she won her first World title in 2023, and instead took on the 100m breaststroke, where she scored a somewhat surprising silver in Singapore.

On top of her breaststroke prowess, Douglass threw down three 100m freestyle relay splits of 52.5 or faster, unheard of for a breaststroker. In the final race of the championships in the medley relay, she split 1:04.2 on the breaststroke leg, while Walsh swam 54.9 on fly, two of the fastest in history, to help the Americans break the world record and finish the championships on top of the medal count.

In the short course venue, Walsh and Douglass were the stars of the show at the three stops of the World Aquatics Swimming World Cup. After Walsh broke her own world record in the 50m butterfly at the first stop in Carmel, she held a steady lead over Douglass in the points standings, breaking World Cup records in the 100m butterfly and 100m IM, as well as making some noise in the 50m backstroke.

Douglass shone by continuing her dominance in the 100m and 200m breaststroke, remaining undefeated in those events as she continued to refine her 100m speed each week.

Using the 100m freestyle as her third event, Douglass first broke the world record in Westmont, and repeated that the following week in Toronto to become the first woman to break 50 seconds in the event, securing her overall win over Walsh.

The dominance, power, and versatility both have shown in long course and short course hasn’t been seen often and any conversations around this “new era” of the sport, always end up using these two as the example for what is possible day to day. No longer do fans need to wait until the end of the year to see the athletes at their peak, they are swimming fast all year round.

Australia, USA Go Toe-to-Toe in Relays in Singapore

The two most dominant swimming nations of this generation put on another show in 2025. Night after night at the World Aquatics Championships in Singapore, the green and gold went toe to toe with the red, white, and blue, and audiences in the arena were rewarded with a treat each time.

It started in the women’s 4x100m freestyle relay, where the Australians have dominated, holding the Americans’ number every year since 2018. Even with a new cast of characters and the Americans’ most stacked team to date, senior newcomer Olivia Wunsch ran down the Olympic silver medalist in the 100m freestyle, Torri Huske, to secure the gold medal once again. Not long ago, in 2022, Mollie O’Callaghan and Meg Harris were the rookies filling in for the veterans on the relay, and three years later, they were the veterans leading rookies Wunsch and Milla Jansen to another gold.

Just a few minutes later in the men’s race, the Americans once again looked on their way to the gold, behind the new veterans Jack Alexy and Chris Guiliano, but when Kyle Chalmers dove in and immediately drew even with rookie Jonny Kulow, it looked like the same movie we’ve all seen. Chalmers had a similar heroic moment at the 2023 World Championships and 2022 World Short Course Championships and secured the upset win over the Americans, with the Australians throwing down the fastest relay in 17 years.

The women’s 4x200m provided a similar thrill - for seven minutes, the two nations went back and forth, setting up a duel between Olympic gold medalists O’Callaghan and Katie Ledecky. O’Callaghan had been vocal about her pre-race anxieties in the past, but she didn’t show any nerves going against Ledecky on the anchor leg, holding her own and not letting the distance queen get any room on each turn. O’Callaghan showed incredible poise, splitting 1:53.44 to not give Ledecky (1:53.71) any space. For seven minutes, the crowd was roaring, providing an environment that hard core swimming fans crave.

The following night, the Australian men out-dueled the Americans for the bronze in the men’s 4x200m behind some clutch splits from Kai Taylor and Max Giuliani. Despite a 1:43 from emerging superstar Luke Hobson, the Americans wound up fourth, a big disappointment back home, but one that turned the last two days around for the struggling team.

After a heroic mixed 4x100m free relay gold medal behind big time splits from Patrick Sammon and Kate Douglass, the Americans walked into the medley relays with the old time swagger the swimming community had been used to seeing.

When the superstar women’s team consisting of two Olympic champions and two world record holders of Regan Smith, Kate Douglass, Gretchen Walsh and Torri Huske, won the 4x100m medley relay by three seconds in a new world record, it was a statement swim by the red, white, and blue. Amidst all the turmoil and the talks of the illness, the team was still the best in the world and swimming faster than ever. 

Lukas Martens Finally Breaks the Vaunted 3:40 Barrier

When Ian Thorpe first swam 3:40 back at the 2000 Olympics on home soil in Sydney, it seemed only a matter of time before he would break that barrier and put up a 3:39. Alas, it never happened in Thorpe’s career, and the rest of the world struggled to match his torrent pace in the years following.

Paul Biedermann was able to go 3:40.07 at the Rome World Championships in 2009, but after Sun Yang got oh-so-close in London 2012 with a 3:40.14, we didn’t see a swim inside 3:41 again until 2023.

Germany’s Lukas Martens finally made the 3:39 appear on a scoreboard in April 2025 at the Stockholm Open - taking on a different approach that finally worked. While Thorpe even split his 400m world record back in 2022, and Biedermann negative split his from 2009, many of the following 400m champions tried to emulate that race strategy, more often than not flipping in front of world record pace at 200 meters at around 1:49, but finding themselves unable to match the closing speed.

Racing rather than pacing would take precedence in major 400m finals, with the winning time often coming around 3:42 and 3:43 between 2011 and 2024, but when Martens finally broke through in 2025, his opening 200m speed of 1:47 was enough to set him apart. The pace was torrent, and it certainly paid a price - Martens just barely broke the barrier with a 3:39.96 as he finally erased Biedermann’s record off the books.

It was a momentous moment for swimming; so many before had tried and failed to break 3:40 with the world record pace catching up and winning every single time. But Martens made it happen, and launched a new race strategy to the 400m freestyle where more could join the sub-3:40 club in the coming years.