Summer McIntosh set for 400m freestyle final clash with Ledecky, Titmus at aquatics worlds

With nine different events on tap on the first day of swimming competition at the World Aquatics Championships on Sunday morning in Fukuoka, Japan, there was little doubt that the fourth and fifth heats of the women's 400-metre freestyle preliminaries would serve as the highlight.

Within the span of 10 minutes, former world record holder Ariarne Titmus of Australia breezed to a first-place finish in the fourth heat with a time of 4:01.39, setting the stage for American swimming legend Katie Ledecky (4:00.80) to edge 16-year-old Canadian phenom Summer McIntosh (4:01.72) in the fifth heat. Germany's Isabel Gose was the next closest competitor with a time of 4:03.02.

For the 26-year-old Ledecky, the 400m freestyle final will serve as her first opportunity to tie Michael Phelps's record of 15 gold medals at the World Aquatics Championships, which she will have more chances to add to as the favourite for both the 800m and 1,500m freestyle events later this week.

The seven-time Olympic gold medallist was denied an eighth at the Tokyo Olympics in 2021 when Titmus topped the podium, then saw her world record time of 3:56.46 — set at the 2016 Games — fall to the now 22-year-old at the 2022 Australian Swimming Championships, with Titmus clocking in at 3:56.40.

WATCH | Stacked field set to compete in women's 400m freestyle:

While a then-14-year-old McIntosh set a Canadian record of 4:02:42 to finish fourth at the Tokyo Olympics — edged by China's Li Bingjie who nabbed the last spot in Sunday's final — the Toronto native quickly staked her claim as a force to be reckoned with by breaking the four-minute mark for the first time in a silver-medal performance at last year's worlds in Budapest, Hungary, out-touched by Ledecky.

From there, McIntosh tacked on two more sub-four-minute times at the Commonwealth Games in August and the 2022 U.S. Open Swimming Championships in December, before blowing the roof off the Toronto Pan Am Sports Centre at the Canadian trials in March with a world record time of 3:56:08.

WATCH | McIntosh breaks 400m freestlye world record:

McIntosh followed up that record with a world record time of 4:25.87 in the 400m medley just days later, an event she will be competing in at the end of the week in Fukuoka.

Ella Jansen, 17, of Burlington, Ont., finished 22nd overall with a time of 4:12.77.

While McIntosh is the focal point of the Canadian team, plenty of stars were also in action on Sunday for a swimming unit that won a national record 11 medals last year in Budapest.

The 20-year-old began his competition with a time of 23.36 seconds for a fifth-place result in an extremely quick eighth 50m butterfly heat, and finished 15th overall among the 92 competitors.

WATCH | Liendo gunning for gold:

Montreal's Ilya Kharun, 18, followed that up with a personal best time of 23.27 — matching Liendo's Canadian record — to claim fourth-place in his heat and ninth overall.