Swimmers from Sweden, Hungary and the United States set new world record in various events at the World Swimming Competition in Kazan, Russia, while China snatched the bronze on the second day, the Xinhua News Agency reported.
Sarah Sjostrom from Sweden broke the world record in the 100m butterfly for the second time while trying to defend her title with the record 55.64 seconds. She improved her previous world record by 0.1 second, which she herself set on Sunday, Aug. 2.
Veteran Jeanette Ottesen from Denmark took the silver in 57.05, while China's Lu Ying came third in 57.48.
"I swam slower than I did in the semis earlier," said Lu, runner-up of the event at the London Olympic Games. "I expected a better time."
Hungary's swimming "Iron lady" Katinka Hosszu also rewrote a new record in the women's 200m individual medley, clocking in at 2:06.12, which was 0.03 second faster than the previous record set at 2009 Rome Worlds by American Ariana Kukors.
Japanese Kanako Watanabe got the silver with 2:08.45, followed by British swimmer Siobhan Marie O'Connor at third with 2:08.77. China's Ye Shiwen, winner of the event at the London Games, finished eighth in the event.
Ye, who looked exhausted after the final, left without a word.
American swimming star Katie Ledecky set the new world record at the women's 1,500m freestyle with a time of 15 minutes 27.71 seconds in the heats, shaving 0.65 seconds off the mark she herself set in Australia in 2014 at the Pan Pacific championships.
It was the fourth time the American swimmer has broken the record in the 1,500m. She will have a chance to improve the record again in the final.
Meanwhile, Britain won its first swimming gold when Adam Peaty finished first in the men's 100m breaststroke with 58.52, followed by South Africa's Olympic champ Cameron Van Der Burgh at 58.59, with Britain's Ross Murdoch in third with 59.09.
French Olympic champion Florent Manaudou dominated the men's 50m butterfly with a winning mark of 22.97, with Brazil's Nicholas Santos coming in second in 23.09, followed by Hungary's Laszlo Cseh with bronze in 23.15.
China's swimming superstar Sun Yang led the 200m freestyle heats with a 1:46.00 finish on Aug.3 and ranked fifth in the semifinal with 1:46.17.
U.S. star Ryan Lochte got the semis in 1:45.36.
"I think I will do better in tomorrow's final," Sun, who won the 400m free on Aug. 2, said. "I expect a top three finish."
China's Fu Yuanhui ranked fourth in the women's 100m backstroke semifinal, qualifying her to the finals, while Xu Jiayu finished sixth in the semifinal to gain entry in the men's 100m back final. Shi Jinglin also made it to the final of 100m breaststroke.