American Katie Ledecky set a second world record in two days by shattering her own 1500-metre freestyle record at the Pan Pacific Championships on Sunday.
The 17-year-old schoolgirl smashed her record by almost six seconds with a time of 15 minutes 28.36 seconds, to claim her fifth gold medal at the Gold Coast meet. (Â Michael Phelps Wins 100m Butterfly Gold, Katie Ledecky Smashes Own World Record)
It was only in June that Ledecky had set the previous record in the 1500 metres, a non-Olympic event, with a time of 15:34.23.
On Saturday the teenager beat her 400m freestyle world record at the Gold Coast meet, clocking 3:58.37 to eclipse her previous mark by 0.49sec.
Ledecky holds the world records in the 400m, 800m and 1500m freestyle, making her the first woman since US distance great Janet Evans to hold all three records at the same time.
"I knew it was my last race of the meet and the last race of the season, and I had a really good season and I wanted to finish on a good note," Ledecky said.
"I didn't want to walk away from the meet feeling that was just okay. So I just dug in deep over the last 50m.
"It was probably one of my most painful races. It was painful, but it pays off in the end, so I'm happy.
"I am really enjoying the journey and just enjoying each step, so hopefully there are a few steps left."
Ledecky has won the 200m, 400m 800m and 1500m freestyle golds at the Pan Pacs and was also part of the American women's winning 4x200m freestyle relay team.
"I would say it's tied with the 400m world record but the 1500m is not a huge priority of mine because it's not an Olympic event, so it's just this year and next year (worlds) that I will probably swim it," she said.
"It's not a huge priority of my training so I didn't really know what to expect. But the mile (1500m) is certainly one of my favourite events and it's the last day of the meet."
Ledecky beat New Zealand's Lauren Boyle by more than 27 seconds in winning the 1500m gold, and was well under world record pace during the middle stages of the 30-lap final.