Chase Kalisz got things rolling, claiming the first U.S. gold at the Olympic pool. By the time the morning was done, the powerhouse team had a whole bunch of medals. Six of them in all, quite a start Sunday for the Americans in the post-Michael Phelps era.
"I'm happy to be here and kick the U.S. off," said Kalisz, who won the 400-meter individual medley.
There was room for others to shine, as well.
Host Japan won a swimming gold, Tunisia claimed a surprising spot atop the medal podium, and the mighty Australian women set the first world record of the competition in the 4x100 freestyle relay.
The Americans certainly had no complaints about their opening-day performance. In Phelps record-setting career, which encompassed five Summer Games, they never won six medals in the first session of finals.
"A pretty good start for the U.S.," said Kieran Smith, who in his first major international meet snagged a bronze in the men's 400 freestyle. "We executed today. I'm really proud of us."
The Aussies, who hope to challenge America's dominance in the pool, picked up three medals Sunday.
The free relay was never in doubt, not with a dynamic quartet that 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. At the medal ceremony, the sisters touchingly draped their medals around each other's neck.
The silver went to Canada in 3:32.78, while the Americans capped their morning with one more medal to surpass their best first-day haul from the Phelps era (five in both 2004 and 2008).
With Simone Manuel anchoring the relay, they touched just behind their rivals to the north in 3:32.81.
Kalisz was the first U.S. medal winner of the Tokyo Games, and Jay Litherland — who was born in Osaka — 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.
In the 400 free, 18-year-old Tunisian Ahmed Hafnaoui was the stunning winner from lane eight, his victory punctuated with loud screams that could be heard throughout the largely empty arena.
"I was surprised with myself," said Hafnaoui, who joined Ous Mellouli as a gold medalist from the north African country. "I couldn't believe it until I touched the wall and saw the 1 (on the scoreboard)."