Kira Toussaint became the first swimmer to set a new world record this International Swimming League season as London Roar and Energy Standard edged towards the final.
The Dutch athlete, competing for London Roar, set a blistering time of 25.60sec to win the women’s 50m backstroke in the first ISL semi-final.
Brazilian Etiene Medeiros had held the short-course world record since 2014, with 25.67.
That race was one of seven won by London Roar in Budapest today, although their only women's victory.
With 20 of the match's 39 races complete, they sit second on 270 points - well clear of Tokyo Frog Kings in third on 208.
Defending champions Energy Standard lead the way on 291, while New York Breakers are a distant fourth with 114.
The top two teams will reach the final.
The three swimmers with the most ranking points all belong to the defending champions, underlining their dominance.
Sweden's Sarah Sjöström - last season's Most Valuable Player - won all four races she took part in today.
The triple Olympic medallist at Rio 2016 won the women's 100m butterfly and 50m freestyle, and brought the Energy Standard team home to win the 4x100m medley and 4x100m freestyle relays.
Sjöström has 35 ranking points, 15-year-old Italian Benedetta Pilato has 23.5 and Australian Emily Seebohm has 22.
South African Chad Le Clos and Frenchman Florent Manaudou also joined Seebohm and Sjöström as Olympic gold medallists to win races for the Parisian franchise today.
The remaining 19 races are set to be completed tomorrow, before the second semi-final gets underway.