Michael Phelps won a fourth consecutive men's 200-metre individual medley on Thursday, claiming the 22nd Olympic gold of his career in Rio de Janeiro, while the women's 100m freestyle resulted in an astonishing tie.
Phelps was trailing after the first two legs but took the lead during the breaststroke and moved clear in the freestyle to win in 1 minute 54.66 seconds. He became the first swimmer to win the same event in four consecutive Games and just the third ever in any sport.
"Every single day I'm living a dream come true," Phelps said after the race. "As I kid I wanted to do something that nobody had ever done before. I'm enjoying it."
Japan's Kosuke Hagino, winner of the 400m medley came second in 1:56.61 and China's Wang Shun took the bronze. Phelps' American team-mate and old rival Ryan Lochte finished outside of the medals.
In the women's 100m freestyle, 16-year-old Canadian Penny Oleksiak and the American Simone Manuel both swam an Olympic record of 52.70 seconds to share gold ahead of Sweden's Sarah Sjostrom. In winning, Oleksiak also became the first individual gold medallist born in the 2000s.
"This is amazing, to tie for a gold," Oleksiak said. "I never thought I'd win. She deserves it as much as me."
Another American, Ryan Murphy completed the backstroke double by adding the men's 200-metres to his 100m crown, seeing off Australian world champion Mitch Larkin.
Japan's Rie Kaneto won the women's 200m breaststroke by holding off Russia's Yulia Efimova, who had previously won silver over 100m.
Phelps and Lochte were expected to duel for the medley honours, but to the delight of the crowd, it was Brazil's Thiago Pereira who led after the butterfly. Lochte edged in front after the backstroke with Pereira tieing for second with Phelps.
But in the breaststroke Phelps made the decisive move, easing away 25 metres into the lap and never looking back. He powered home in the freestyle as behind him Hagino charged into silver from fifth, while world-record-holder Lochte faded.
Phelps returned to the pool around 30 minutes later for the semi-finals of the men's 100m butterfly. He qualified fifth fastest overall with Singapore's Joseph Schooling coming first.
In between Phelps' races there was the remarkable women's 100m freestyle final which started with favourite Cate Campbell going out under world record pace. However, she faded in the second 50 metres leaving the race wide open.
Manuel moved up from third but Oleksiak charged alongside her from seventh and the pair could not be separated at the touch. Oleksiak now has a gold to go with her butterfly silver and two relay bronze from the Games while the medal is Manuel's first.
"My first gold at my first Olympics is really a surprise," Manuel said. "I'm blessed to be on the medal stand."
Sjostrom was third to complete her collection of a medal of every colour from Rio, while Bronte Campbell, Cate's sister, missed out on bronze by five hundredths.
Kaneto took the lead in the last 50 metres of the 200m breaststroke and won in 2:20.30. Efimova, a controversial figure in Rio for having twice been banned for doping, faded having made ground in the last lap.
"I'm delighted," Kaneto said. "Definitely this feels the heaviest medal of the various medals I've got. This was a lifetime ambition."
Efimova eventually finished more than a second behind, with bronze going to Shi Jinglin of China.
Murphy won in 1 minute 53.62 seconds to claim his second gold of the Rio Games. Larkin, who failed to medal in the 100m, took silver 0.34 seconds behind with bronze going to Russia's Evgeny Rylov just 1 hundredth further back.
Larkin had led after 50m but from then on Murphy dominated and never looked in danger of being caught.
"That one was very painful but I wanted it bad," Murphy said. "The 100m backstroke comes more naturally for me. "[The] 200m back is an event I really have to dig deep for. This medal means a little more to me."
In the other session semi-finals, reigning champion Florent Manaudou of France paced the 50m freestyle, while home fans cheered on Brazil's Bruno Fratus, who qualified joint sixth.
Katinka Hosszu of Hungary, chasing a fourth gold of the Games, topped the women's 200m backstroke sem-final while reigning champion Missy Franklin's miserable week continued as she missed out, placing 14th.