The phenomenal Katie Ledecky saved her best for last, while Michael Phelps tasted a final defeat for the first time at Rio 2016 on the penultimate day of swimming action.
Ledecky was victorious in the 800 metre freestyle by an almost preposterous margin, the 19-year-old lowering her own world record to eight minutes, 4.79 seconds as she claimed her fourth gold of the Games.
Nearest challenger Jazz Carlin (Great Britain) was more than 11 seconds back in claiming silver, with Boglarka Kapas of Hungary taking bronze.
Phelps had to settle for a dramatic three-way tie for second in the men's 100m butterfly final, an event the 22-time gold medallist won at the 2004, 2008 and 2012 Games. Joseph Schooling stormed clear of the field to triumph in 50.39 seconds and earn Singapore's first Olympic gold, with Phelps, Chad Le Clos and Laszlo Cseh all three-quarters of a second back.
Friday's two other finals were won by Americans. Maya Dirado pipped Katinka Hosszu by six hundredths of a second in the women's 200m backstroke final, denying the Hungarian her fourth gold.
Anthony Ervin, meanwhile, triumphed in the men's 50m freestyle at the age of 35, some 16 years on from winning the same event at the Sydney Olympics.
RACE OF THE DAY
While Phelps' defeat would normally have guaranteed all the headlines, it is a sign of the passing of the baton in US - and indeed Olympic - swimming that Ledecky rightly claimed centre stage.
In storming to victory, she became the first-ever teenager to defend an Olympic swimming title, and made it a perfect 15 from 15 in individual events at major international meets.
In typical Ledecky fashion, she blew her competition out of the water, opening up a 2.59-second lead at the 200 metre mark and building on that every 100 metres until she touched the wall, as she broke her own mark of 8:06.68 set earlier this year.
Her split at the halfway point of the race (4:01.98) would have placed her fourth in the women's 400m freestyle final on Sunday. Ledecky's final time was faster than 20 of the men's 800m splits in Friday's preliminary heats of the 1500m freestyle.
Ledecky had been tipped to set a new benchmark in the 800m free and did not disappoint. Schooling's time in the 100m butterfly represented a new Olympic record, the Singaporean taking that honour from Phelps.
QUOTES OF THE DAY
"I told him, 'Four more years?' and he said, 'No way.' If he changes his mind, that would be fun. I like racing Michael" - Schooling reveals that he asked Phelps to reconsider his retirement after denying him his 23rd career Olympic gold.
"I saw second next to my name and then I looked up again and then I looked over at Laszlo and Chad like, huh, we all tied for second, that's kind of cool" - Phelps is typically philosophical in defeat after signing off his last individual race at the Games.
"Me, Jeanette Ottesen and Aliaksandra Herasimenia got on our bus, two hours before the start of our race, to come down to the pool. It took us to the Olympic Stadium, which happens to be 40 minutes in the opposite direction to the pool," - Fran Halsall of Great Britain explains the unusual circumstances that resulted in the women's 50m freestyle semi-finals being delayed.
The Rio 2016 swimming programme concludes on Saturday with four finals. Gold medals are up for grabs in the women's 50m freestyle and men's 1500m freestyle before two 4x100m medley relays close the show.