Katie Ledecky is expected to set world and Olympic records in all three of her individual events at Rio 2016 and did not disappoint on Sunday.
In her first individual event, the 400 metre freestyle preliminaries, Ledecky flirted with breaking her own world record (3:58.37) before settling for a new Olympic best of 3:58.71.
France's Camille Muffat, who died in a helicopter crash last year, had set the previous mark of 4:01.45 at London 2012.
Ledecky said she knew the crowd was into her pursuit of the record.
"I could hear that a little bit, but I didn't pay attention to it," the 19-year-old told NBC.
A two-time world champion in the 400m free, Ledecky now owns nine of the 10 fastest times in the women's 400m history. She will swim in the finals of the event later on Sunday.
"I'm just going to get some rest now, and focus on how I'm going to swim it," Ledecky added.
Ledecky already has one medal to put in her trophy case, a silver medal she earned in the 4x100-metre freestyle relay on Saturday. Still to go for Ledecky on the individual side are the 200m and 800m free events.