SINGAPORE, Singapore (AFP)—Swimming sensation Summer McIntosh won a second world gold in as many days as she triumphed in the 200m medley on Monday, with 12-year-old prodigy Yu Zidi fourth.

The 18-year-old Canadian McIntosh came home in 2min 06.69sec, with Alex Walsh of the United States second (2:08.58) and Canada’s Mary-Sophie Harvey third (2:09.15).

China’s Yu was just outside the medals in 2:09.21, having been fastest off the blocks and in third place before fading a little.

McIntosh came to Singapore in red-hot form.

She then romped to the 400m freestyle crown on Sunday’s opening day of competition and is on track to join Michael Phelps as the only swimmer to win five individual titles at a single world championships.

“Going into the race tonight my goal was to put my head on the wall first, so to get that done is good,” said McIntosh.

“I’m not super-happy with the time, but honestly, at a world championship, my goal is just to go as fast as I can.

“Still happy with the gold and hoping to keep up my streak next time.”

The Olympic champion and world record holder came into the 200m medley as strong favourite.

The teenager smashed Hungarian Katinka Hosszu’s decade-old world record at the Canadian trials in June with a sizzling time of 2:05.70.

At the trials she also bettered her own 400m medley world record -– her third world mark in a matter of days.

McIntosh was one of the stars of the swimming at her breakout Olympics in Paris a year ago.

She won three golds, including the 200m and 400m medley double.

In Singapore she will also race in the 400m medley, 200m butterfly and 800m freestyle.

Chinese schoolgirl Yu, who juggles swimming with homework, threatened to win an astonishing world medal before she even becomes a teenager.

Yu, who turns 13 in October, will also compete in Singapore in the 400m medley and 200m butterfly.

The minimum age at the championships is 14 but younger swimmers can compete if — like Yu — they meet the qualifying standard.