Katie Ledecky has improved on her own world record in the 800-metre freestyle, finishing in 8 minutes 6.68 seconds at the Arena Pro Swim Series in Austin on Sunday.
The 18-year-old American beat her previously time of 8:07.39 set at the 2015 world championships in Russia.
Becca Mann finished a distant second on Sunday, almost 20 seconds behind Ledecky with a time of 8:24.49.
"It was exciting," Ledecky told reporters. "It's always exciting when you can get pushed along by a crowd like this in Austin.
"I was feeling good going into it; I knew I had some good swims this weekend. Whenever I get going like that, I get into a good rhythm with my freestyle.
"My stroke just feels good the whole weekend once I have one or two really good freestyle swims."
The Olympic gold-medallist broke the record in 2013, taking over from Great Britain's Rebecca Adlington and has gone on to improve it on three different occasions by a total of over seven seconds.