The opening day of events gathered impressive crowds, with schoolchildren from all over the host city visiting the Brazilian Paralympic Training Centre.

Brazil's highlight came in the shape of S6 swimmer Talisson Glock, who twice broke the national record in the men's 50 metres butterfly - once in the morning’s heats, and then again in the final.

"I'm delighted," Glock said.

"It’s not even one of my principal events and I managed to break the national record."

Glock is a two-time Paralympic medallist, having won a silver and bronze at the Rio 2016 Games.

He will be back in action tomorrow, competing in the 100m backstroke and 200m individual medley events.

Today’s races set the bar high for the rest of the World Series, particularly the men’s 100m butterfly, in which two Brazilian records were broken in the S8 and S9 classifications.

S8 swimmer Gabriel Cristiano was visibly ecstatic at the end of the final, securing the national record with a time of 1 min 4.46sec.

"I broke my personal best twice today, this final was perfect," he said.

"We’re on the right track, our team is really well disciplined and I think congratulations are in order."

Elsewhere, S9 athlete Camille Rodrigues ended up with bronze in the women’s 400m freestyle, after being unable to improve on her strong showing in the morning’s heats.

"I gave it my best, but unfortunately my time was a little higher this afternoon," Rodrigues said.

"Now, we need to keep working hard.

"I have the 100m backstroke tomorrow and I’m feeling confident."

Of the visiting nations, Chile got off to the best start, with Alberto Abarza taking gold in the men’s 200m freestyle and Kiara Soto winning silver in the women’s 100m butterfly.

Besides the 100m backstroke and 200m individual medley, tomorrow’s schedule also includes the 50m freestyle, 50m backstroke, as well as the 150m individual medley. 

In the 200m individual medley, all eyes will be on Argentina’s Daniela Gimenez, who makes her debut in this year’s competition.

The World Para Swimming World Series has returned for a second year following an inaugural edition in 2017.

Athletes take part in a number of events across the season, hosted in Europe and the Americas, with the swimmers' performances ranked on a points scale to determine the final champions.

Daniel Dias, Brazil’s most decorated Paralympian, came away with the 2017 overall men’s title, while Italy’s Monica Boggioni finished in first place among the women.

This year’s World Series has already seen events held in Denmark’s capital Copenhagen and Indianapolis in the United States with the São Paulo leg marking the third of the season-long tournament.

Competition will then head back to Europe for meetings in Italian town Lignano Sabbiadoro, English city Sheffield and Germany’s capital Berlin.

Action in São Paulo is due to conclude on Saturday (April 28).