The Chinese swimmer completed a men’s backstroke double by following his success over 100m with victory over 50m.

It was a powerful performance from Qin who stormed to victory in 26.29sec, beating defending champion Nic Fink of the United States.

Fink touched the wall in 26.59 for silver before Sun Jiajun added a further medal to China’s tally with bronze in 26.79.

Qin then made the difference in the mixed 4x100m medley relay final as he produced a fine second leg after taking over from Xu Jiayu to put China in control.

Zhang Yufie and Cheng Yujie managed to maintain China’s lead as the team triumphed in 3:38.57.

Australia had to settle for silver in 3:39.03. while the US featuring Fukuoka 2023 gold medal-winners Ryan Murphy and Kate Douglass posted 3:40.19 for bronze.

"This is our time, it's a great time," said Zhang, as reported by Olympics.com.

"I have a beautiful and a wonderful team.

"This gold medal means a lot to us because as you know, last year we won this event and also broke the world record.

"This event for us means the future potential is going to be better and better."

Ahmed Hafnaoui bounced back from his disappointment of missing out on men's 400m freestyle gold by triumphing over 800m.

The Tunisian Olympic champion gained his revenge over Australia’s Sam Short by clinching top spot in 7:37.00.

Short picked up silver in 7:37.76, while defending champion Bobby Finke of the US came home in 7:38.67 for bronze.

Marchand captured his second gold medal in Fukuoka by clinching the men’s 200m butterfly title.

Boosted by his 400m individual medley in a world record time earlier this week, Marchand delivered another impressive showing to top the podium again as he finished in 1:52.43.

Krzysztof Chmielewski of Poland clocked 1:53.62 for silver, while home favourite Tomoru Honda sealed bronze in 1:53.66.

Double Olympic champion O'Callaghan shaved 0.13 off Italian Federica Pellegrini’s previous world record in the women’s 200m freestyle after touching the wall in 1:52.85.

Australia's Ariarne Titmus, the winner in the 400m freestyle, came second in 1:53.01, while Canada’s Summer McIntosh completed the podium in 1:53.65.

"If I'm being honest, I feel shaken. I was just expecting to have fun," said O'Callaghan.

"Coming away with the record is just amazing."

The first medals were presented in the high diving as Rhiannan Iffland of Australia saw off the Canadian challenge of Molly Carlson and Jessica Macaulay to win women’s gold.

Iffland registered a winning score of 357.40 points, while Carlson notched 322.80 for silver and Macaulay earned 320.95 for bronze.

The Netherlands and Spain will meet in the women’s water polo gold-medal match after emerging victorious from tight semi-finals.

The Dutch team edged Italy 9-8 before Spain defeated Australia 12-10.