Home contender Vladimir Morozov and Sweden's Sarah Sjostrum set World Cup records on day one of the International Swimming Federation (FINA) World Cup series in Russia.
The 26-year-old Morozov, world record holder in the 100 metres individual medley, won the men's 50m freestyle in 21.49 seconds from Michael Andrew of the United States and Ukraine's Andrii Govorov, who clocked 21.99 and 22.03 respectively in Kazan's Aquatics Palace venue.
It was his first long course victory in an individual event since 2014.
"This is very close to my personal best," Morozov said.
"It's nice to start the season with a good race and a good win, notwithstanding the fact that I arrived from the United States only three days ago - I feel like it's 7am.
"It will be interesting to see how the 100m free will go tomorrow."
Sjostrum, last year's overall World Cup winner, set the other World Cup record on the night as she won the women's 100 m freestyle in 23.83.
Ranomi Kromowidjojo of The Netherlands touched second in 24.55, while her compatriot Femke Heemskerk placed third in 24.64.
"I'm very happy with this time," she said.
"I felt really strong on the 50m free and I'm pleased with that.
"Three weeks ago I did the European Championships so I had three weeks of recovery with easy training."
The "Iron Lady" from Hungary, Katinka Hosszu, earned two golds and one silver medal.
In the 200m butterfly she won a tough race against team-mate Zsuszanna Jakabos, clocking 2:08.93.
Jakabos was second in 2:09.13, with Russia’s Lada Bragina third in 2:18.88.
The men’s 100m breaststroke provided another close finish as Anton Chupkov of Russia won in 59.53 from halfway leader Felipe Lima of Brazil, who took silver in 59.73.
Arno Kamminga of The Netherlands took third place in 59.99.
Last year's overall men’s World Cup winner, Chad 'e Clos of South Africa, had to settle for silver in the men's 100m butterfly.
He touched second in 52.00, sharing the silver medal with Egor Kuimov of Russia, with Michael Andrew of the US taking gold in 51.96.
"My season finished quite early - at the Commonwealth Games in April," Le Clos said.
"Then, I started training for the upcoming short course World Championships and for the Olympic Games.
"A lot of hard work, I'm excited to see what happens.
"This is my first competition since April in long course."