Adam Peaty claimed the first medal for Team GB at the Rio 2016 Olympic Games by winning gold in the men's 100m breaststroke in a world record time of 57.13 seconds. The 21-year-old led from start to finish to become Great Britain's first individual Olympic swimming champion since Adrian Moorhouse in 1988.
The world record holder finished half a second ahead of Cameron van der Burgh of South Africa and American Cody Miller to add Olympic gold to his three world titles in a dominant display.
"It's surreal to get Team GB's first gold," he told BBC Sport. "This is a product of seven years of work. I came out tonight, did the first 50m easy and then gave it everything I've got. I did it for my country, that means so much to me.
Wales' Jazz Carlin continued a stunning evening in the pool with silver in the women's 400m freestyle, to add to Peaty's earlier success. The 25-year-old finished behind Katie Ledecky, who smashed the world record on her way to winning gold, while Leah Smith of America took bronze.
"I honestly can't believe it," she told BBC Sport. "I am on the edge of tears because it's not really sunk in. I knew it was going to be a tough race. Katie breaking the world record I just tried to stick with it and have a good race and I didn't want to be at the back, I was wanted to be up there chasing for medals. I'm so happy.
"Four years ago I was sitting in the aquatics stadium watching from the sidelines, cheering everyone on and now I have a medal. I was watching Adam break the world record and win gold and I was pumped before I swam I knew I had to stay relaxed and calm before the race. I'm gobsmacked."
James Guy will attempt to add to the British success in the pool after qualifying for Tuesday's men's 200m freestyle. The world champion was the eighth fastest to progress to the final, yet he is an outsider for a medal behind Son Yang of China and world record holder Paul Biedermann.
"I would have liked to have gone a bit faster and I am not sure what happened. I think you need a 1:45 [to get a medal] but for me it's about getting the process right," he told BBC Sport. "The first day was a write-off. It went better than the 400m. I've always set my eye on the 400m free and I've tried to do the same thing here and I think it's gone ok."