Leon Marchand was fastest in the 200 metres individual medley (IM) heats at the world championships in Singapore on Wednesday as France's Olympic hero made his long-awaited return to the world stage.
The four-time Olympic champion glided to a time of one minute, 57.63 seconds, 0.11 ahead of Japan's Kosuke Makino, in an encouraging start to his bid for a third world title in the event and a possible world record.
Exhausted after the Paris Games, Marchand skipped the short course world championships in Hungary last December and suffered injuries before returning to the pool for the TYR Pro Series in Florida in May.
He is swimming a reduced programme in Singapore, focusing on the 200 and 400 IM alone for individual events as he works through what he calls a "transition year".
Summer McIntosh is on the other end of the spectrum as she looks to match Michael Phelps's record of five individual gold medals from a single world championships.
Having already won two of them, the 200 IM and 400 freestyle, the 18-year-old Canadian started her bid for the third in the 200 butterfly on day four with the fastest swim in the heats (2:07.07).
American Regan Smith was third quickest into the semifinals, more than a second behind McIntosh, while China's 12-year-old wunderkind Yu Zidi was fifth fastest (2:08.95).
Three years after winning the 100 and 200 freestyle in Budapest, Romania's David Popovici is eyeing another double in the sprints.
The 20-year-old Olympic bronze medallist was fastest in the 100 heats in 47.41, the morning after his 200 triumph in Singapore.
Olympic champion and world record holder Pan Zhanle (47.86), and runner-up Kyle Chalmers (47.48) were among eight swimmers under the 48-second barrier on the way to the evening semifinals.
Canada's Kylie Masse qualified fastest for the women's 50 backstroke semifinals with a time of 27.46. Regan Smith and fellow American Katharine Berkoff, who medalled in the 100 behind winner Kaylee McKeown, were also safely through.
Australia's world record holder McKeown skipped the event.
The session finished with a shock as Olympic champions the United States failed to reach the final of the 4x100 mixed medley. Several US swimmers have not been at their best in Singapore after a bout of food poisoning swept through the team's pre-meet camp in Thailand.
France and Britain also missed out but Italy emerged quickest in the heats in a time of 3:42.19, ahead of the Netherlands and China. Fourth-quickest Australia are also a chance for a medal in the evening final.
Five golds will be up for grabs in the evening session, with Australian Olympic champion Mollie O'Callaghan bidding for a second 200 freestyle title.
The men's 800 freestyle final will feature Ireland's Olympic champion Daniel Wiffen battling a stacked field including Australian Sam Short and Tunisia's Ahmed Jaouadi.