U.S. swimmers on Monday added two more medals following their historic opening day performance Sunday at the Tokyo Olympics.

Australia's Ariarne Titmus defeated American Katie Ledecky Monday to win one of the more anticipated races of the Summer Games. Ledecky earned a silver medal in 3:57.36 -- the fourth-fastest time ever recorded. 

Following her loss, Team USA won gold in the men's 4x100 freestyle relay – led by Caeleb Dressel. 

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United States men's 4x100m freestyle relay team of Caeleb Dressel, Blake Pieroni, Bowen Beck and Zach Apple, celebrate with their medals after winning the gold medal at the 2020 Summer Olympics, Monday, July 26, 2021, in Tokyo, Japan. (AP Photo/Matthias Schrader)

"I felt good the whole way, I knew I had to get my hand in the wall first and get some clean water,'' Dressel said, according to ESPN. "And everyone did their job. It's a relay for a reason, it's four guys for a reason, it's certainly not just me. It's certainly not just one guy.''

On Sunday, Team USA swimmers got off to a blazing start. They earned six medals –  one gold, two silver, and three bronze – which were the most won on the first day of the Olympic swimming finals, according to the Wall Street Journal. 

It was seen as a promising start in the post-Michael Phelps era. U.S. men’s team assistant coach Jack Bauerle noted the team made the podium in events they weren't expected to medal.

"It’s obviously a really proud moment," he said, according to the paper. "I can’t really feel anything, I’m so happy." 

In the first event of the day, American Chase Kalisz won gold in the men’s 400-meter individual medley. Kalisz finished in 4:09.42 while Jay Litherland, his training partner at the University of Georgia, earned silver by touching second in 4:10.28.

Japan’s Yui Ohashi won gold in the women’s 400 IM, though two American's still made the podium. Emma Weyant earned the silver, and the bronze went to Hali Flickinger. It was the first time in decades that two American women medaled in the event, according to the Wall Street Journal. 

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"After we saw (Kalisz and Litherland go 1-2), we kind of looked at each other and said, ‘It’s our turn,’" Weyant said. "I think that really got our team going."

In the men’s 400 freestyle, Kieran Smith won bronze in 3:43.94 behind Australia’s Jake McLoughlin and Ahmed Hafnaoui, an 18-year-old from Tunisia who won a surprise gold from lane eight.

Team USA’s final medal of the session, a bronze in the women’s 4×100 freestyle relay, was its least likely -- after the team qualified fifth on Saturday night. 

U.S. women’s team coach Greg Meehan took a gamble by giving the anchor spot to Simone Manuel, the defending gold medalist in the women’s 100 freestyle who failed to make the final of the event at the U.S. Olympic Swim Trials in June. 

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Manuel said she has suffered with "overtraining syndrome" --a condition where athletes experience fatigue, elevated heart rates, and declining performance during usual training --this year, but was "feeling better" in Tokyo. 

She turned in the second-fastest split for the Americans, who finished 0.03 seconds behind Canada in 3:32.81. Australia broke the first world record of the meet, swimming 3:29.69 en route to gold.

The Wall Street Journal and the Associated Press contributed to this report