TOKYO (AP) — Chase Kalisz led a medal haul by the powerhouse American team at the Olympic pool, taking gold Sunday in the men's 400-meter individual medley.
There was room for others to shine, as well.
Host Japan claimed its first swimming gold, and Tunisia also got a stint atop the medal podium.
Kalisz was the first U.S. medal winner of the Tokyo Games, and Jay Litherland made it a 1-2 finish for the Americans by rallying on the freestyle leg to claim the silver. Brendon Smith of Australia earned the bronze.
Kieran Smith grabbed another medal for the American men with bronze in the 400 freestyle. Tunisia's Ahmed Hafnaoui was the surprising winner from lane eight, while Australia's Jack McLoughlin settled for silver after leading much of the race.
The American women also did their part. Japan's Yui Ohashi won gold in the women's 400 IM with a dynamic breaststroke leg, but two Americans were right in her wake.
Emma Weyant earned the silver, while the bronze went to Hali Flickinger.
The mighty Australian women set the first world record of the competition in the 4x100 freestyle relay.
The Aussie quarter included sisters Bronte and Cate Campbell swimming the leadoff and anchor legs, respectively, joined by Meg Harris and Emma McKeon.
McKeon blew away the field on the third leg and Cate Campbell touched in 3 minutes, 29.69 seconds.
The silver went to Canada in 3:32.78, while the Americans capped their morning with one more medal. With Simone Manuel anchoring the relay, they touched just behind their rivals to the north in 3:32.81.
Kalisz, a protégé and former training partner of Olympic great Michael Phelps, touched first in 4 minutes, 9.42 seconds. Litherland was next in 4:10.28, just ahead of Smith (4:10.38).
Kalisz flexed his muscles and then climbed atop the lane rope, splashing the water while a contingent of his teammates cheered him from the stands of the nearly empty Tokyo Aquatics Centre.
"U-S-A! U-S-A!" they chanted.
Kalisz was the silver medalist in the grueling event at the Rio Games five years ago. Now, at age 27, he's the best in the world at using all four strokes.
"That one was the most special type of pain," Kalisz said. "I had vowed that I was going to make that hurt as much as possible and give my absolute best to accomplish this."
Litherland came over to give the winner a hug, having ensured the Americans got off to the best possible start at the pool.
"To come back and do this with Chase means a lot," said Litherland, who finished fifth in the 400 IM at Rio.
After putting their own medals around their necks during a masked-up victory ceremony, Kalisz and Litherland walked around the deck arm-in-arm.
No social distancing for them.
The Americans seized their chance after Japanese star Daiya Seto stunningly failed to advance to the final, having finished ninth in the preliminaries after making a tactical error attempting to save his energy for the medal race.
The finals were held in the morning Tokyo time rather than their usual evening slot, a nod to U.S. television network NBC, which wanted to show the finals live in prime time back in America.
That was the same format used at the 2008 Beijing Games, where Phelps won a record eight gold medals. He retired after Rio, having captured 23 gold medals overall, but the Americans still have plenty of star power for the post-Phelps era.
From the far edge of the pool, Hafnaoui joined Ous Mellouli as a gold medalist from the north African country of Tunisia.
Hafnaoui touched in 43:43.26, followed by McLoughlin (3:43.52) and Smith (3:43.94).
"I sprinted my butt off the last 50 like it was a 50 free," Smith said. "It was a really fun race."
Ohashi helped to make up for Seto's flop in the men's IM. She pulled away in the breast to win 4:32.08.
Weyant gave chase in the freestyle leg but settled for silver in 4:32.76. Flickinger was third in 4:34.90, while Hungarian great Katinka Hosszu, the defending champion, faded to fifth.
"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."