Katie Ledecky of the United States broke her own 1,500m freestyle record in the heats of the world swimming championships in Kazan on Monday.
The 18-year-old, who also holds the 400m and 800m freestyle world records, clocked 15min 27.71sec to better the 15:28.36 secs she swam at the Pan-Pacific Games on Australia's Gold Coast in August last year.
She only recently finished high school in Maryland, but this is the eighth time the teenager has set a world record in her fledgling career.
It is the fourth time the defending champion has broken the 1,500m record having first achieved the feat in Barcelona two years ago on her way to winning the world title.
– W. Champs: Sun Yang claims gold before criticising media
She lowered it again in Texas in June 2014 before bettering it once more in Australia on August 24 last year, the day after setting the current 400m freestyle world record.
"My coach told me to swim the first 900m easy, build over the next 300, then the final 300 was my choice and to be honest, it felt pretty easy," said Ledecky, who came within a second of her 400m record on Sunday.
"I wasn't kicking much and I think breaking the world record is testament to the hard work I have put in and the shape I am in right now.
"I am pretty shocked that I was able to do that."
