The French relay, made up of Maxime Grousset, Charles Rihoux, Charlotte Bonnet and Marie Wattel, won with a time of 3 min 22 sec 80, ahead of Great Britain (3.23.30) and Sweden (3.23.40) .
Wattel, already a silver medalist in the 50 and 100 m butterfly, completed a final high-level length to allow the mixed relay to be crowned.
The 25-year-old Frenchwoman, like Charlotte Bonnet, has already won the gold medal in this discipline at the Glasgow Euro in 2018.
In 2nd place after the third stint, provided by Charlotte Bonnet, 7 hundredths behind the Italians and the Swedes, the French team was able to count on the thunderous stint of Wattel to take control.
Maxime Grousset, who had launched the Blues perfectly by positioning them in the lead, won his second medal after silver in the 50m butterfly.
Monday morning, the Blues, led by Hadrien Salvan, Charles Rihoux, Lucile Tessariol and Béryl Gastaldello, swam the best time in the semi-finals in 3 min 26 sec 19.
France competed in this event without Florent Manaudou, Olympic champion in the 50m in London in 2012, nor the phenomenon Léon Marchand, 20, double world champion in the 200x4 medley and 400x4 medley in Budapest in June, or even the sprinter Mélanie Hénique .
© 2022 AFP