Michael Phelps and Katie Ledecky further enhanced their illustrious reputations at Rio 2016 on Tuesday, the former claiming two more Olympic gold medals to take his record-breaking tally to 21.
Already the most successful Olympian in history by some margin, Phelps triumphed in the men's 200 metre butterfly final to secure the 20th gold of his career.
Chad Le Clos of South Africa had edged out Phelps in the same event four years ago, but on this occasion the South African finished outside the medals as the fast-finishing Masato Sakai and Tamas Kenderesi claimed silver and bronze.
Phelps was not finished there, however, and went on to help the United States to a fourth successive victory in the 4x200m freestyle relay, alongside Ryan Lochte, Conor Dwyer and Townley Haas.
Teenage sensation Ledecky held off Sweden's Sarah Sjostrom to add the 200m freestyle crown to her previous success over 400m. The American appears all but certain to end the week with three golds, given her dominance over 800m.
Tuesday's other gold medallist was Katinka Hosszu, who set a new Olympic record in beating Siobhan-Marie O'Connor by three tenths of a second in the women's 200m individual medley final.
Hosszu has now claimed three golds in Rio, all over different distances. Her previous triumphs came in the 100m backstroke and 400m IM.
RACE OF THE DAY
The renewal of battle between Phelps and Le Clos had been much anticipated, yet the latter was ultimately left behind as two less-heralded names provided the biggest challenge to the victor in a thrilling finish.
Hosszu was not the only swimmer to set an Olympic record on Tuesday. Ippei Watanabe did likewise in the semi-finals of the men's 200m breaststroke.
QUOTES OF THE DAY
"That hurt pretty badly. It's the closest I've come to throwing up at the end of a race," - Ledecky's latest triumph did not come easily.
"I couldn't be happier. Ledecky, she's one of a kind so it feels like a gold to me that I'm after her," - Sjostrom was delighted with her silver.
"Nothing. I've been getting on that Snapchat game. It's been fun," - Lochte's response when asked what he had been doing in the four days leading up to the 4x200m relay final.
Following his outstanding semi-final performance, Watanabe will be the favourite in the men's 200m breaststroke final on Wednesday. There are also golds up for grabs in the women's 200m butterfly, men's 100m freestyle and women's 4x200m freestyle relay.