Sweden's Sarah Sjostrom clocked a world-record 51.71 seconds for her leg of the women's 4x100m freestyle relay final at the World Aquatics Championships on Sunday, but her team was only able to finish fifth.

Sjostrom became the first woman to swim under 52 seconds, beating the previous record of 52.06 sec set by Australia's Cate Campbell in 2016.

It was the only world record to fall on the opening day of the swimming competition in Budapest.

While Katie Ledecky helped steer the US to victory in the relay, with Australia finishing second and the Netherlands third, Sjostrom made history in her stunning opening leg.

"The plan was to go for the world record on the first day, because I know I'm going to be more fresh then than maybe later this week," said the 23-year-old.

"It's also much easier to go for records in the first leg of the relay, so I kind of took the chance.

"I went all out for the first 50, and hoped for the best on the last 50.

"It wasn't really smart swimming, I was just chancing it.

"It's not a perfectly planned race, like when I will swim the individual races later this week."

AFP