Adrian, 23, won the 100-meter Olympic freestyle, lunging to the wall one-hundredth of a second before James "The Missile" Magnussen of Australia.
"I had no idea, to be honest," said Adrian, whose winning time was 47.52 seconds. "I'm a guy that has a lot of speed and I can go out fast and I die a little more than he does. It's a little nerve-racking the second 50. I just had to really focus on it and stay strong."
Soni of the United States set a world record in the 200-meter breaststroke semifinals. She timed 2:20.00, shaving 0.12 seconds off the previous mark set by Annamay Pierse of Canada at the 2009 world championships in Rome.
Also Wednesday, Americans Missy Franklin, Dana Vollmer, Shannon Vreeland and Allison Schmitt won gold in the 4x200-meter freestyle relay with a combined time of 7 minutes, 42.92 seconds. The team set an Olympic gold record and was only 0.84 seconds off the world record mark. The gold medal is the second for Schmitt, Franklin and Vollmer.
Eight female badminton players were kicked out of the Olympics for allegedly trying to throw their matches.
The Badminton World Federation said doubles players from China, South Korea and Indonesia deliberately lost games in order to have better match-ups in upcoming rounds.
Olympic officials gave the federation authority to investigate and discipline the teams, so all eight players were disqualified. The Badminton World Federation rejected an appeal by disqualified South Koreans. Indonesia withdrew its appeal.
The competition continued Wednesday with four previously eliminated teams in the quarterfinals. Those teams were from Russia, Canada, Australia and South Africa.
In women's beach volleyball, two-time defending champs Kerri Walsh Jennings and Misty May-Treanor lost the first set, the first lost set in three Olympics, But they came back to win the second set 21-8 and took the third 15-10 to remain unbeaten in every trip to the Olympics.
In cycling, USA's Kristin Armstrong, who briefly retired after her triumph at the 2008 Beijing Olympics to start a family, won her second straight gold medal in the Olympic cycling time trial, beating Judith Arndt of Germany by more than 15 seconds. Armstrong covered the 18-mile course in 37 minutes, 34.82 seconds.
In women's water polo, the U.S. tied Spain 9-9. Both teams remain tied for first in Group A, with three points from two games.
In gymnastics, Danell Leyva of the United States rallied for the bronze in the men's all-around. He had spectacular routines on both parallel bars and high bar. Leyva joins 2004 champion Paul Hamm as the only U.S. men to win Olympic all-around medals since 1984.
In tennis, Venus Williams lost her third-round match to No. 7-seeded Angelique Kerber of Germany. She still has a shot at a record fourth gold medal in Olympic tennis - she plays doubles with her sister Serena in the quarterfinals Thursday.
Serena Williams advanced to Olympic quarterfinals, routing No. 13 seed Vera Zvonareva 6-1, 6-0. Maria Sharapova, Victoria Azarenka and Kim Clijsters also advanced.
It was a good day for the host nation as well. Britain won its first gold medal when Helen Glover and Heather Stanning won the final in women's pair rowing. Under intense pressure, the favorites established a big lead early in the race and were never threatened. They crossed the line in 7 minutes, 27.13 seconds. Princes William and Harry watched the race.
Americans are still celebrating major victories in gymnastics and swimming. The U.S. won its first team gold in women's gymnastics in more than 15 years. The team had a strong start with a series of picture-perfect vaults. Through the rest of the competition, the women sailed to a final score that was five points higher than silver medalist Russia. It's America's first team gold since 1996.
President Barack Obama personally phoned the women's gymnastics team to congratulate them on their "remarkable success," according to Press Secretary Jay Carney.
The president also congratulated swim sensation Michael Phelps via Twitter. Phelps set the Olympic record for most medals won, helping the U.S. to the gold medal in the 4x200-meter freestyle relay. That brings his medal haul to 19, including a record 15 gold, two silvers and two bronzes.
The Associated Press contributed to this report.