The S5 athlete, vying to defend his overall World Series title, held off strong fields to win both the men’s 50 metres freestyle and 50m backstroke races at the Brazilian Paralympic Training Centre.

"I’m delighted to be back competing, and even happier after today's performance," Dias, a winner of 14 Paralympic gold medals, said.

What made Dias’ performance even more special was the fact that less than 30 minutes separated his two finals.

"For two races which were practically back-to-back, these results are excellent," he added.

"It’s a great way to start off my season."

This morning’s heats started with Chile’s S2 swimmer Alberto Abarza breaking his own Americas record in the men’s 50m freestyle.

Abarza is in superb form at this World Series having also grabbed the first gold medal yesterday in the 200m freestyle.

Additionally, he picked up silver medals today in the 50m backstroke and 50m freestyle, in which he once again lowered his own Americas record.

Abarza ended last year ranked number one in the world in the 50m freestyle S2.

"I feel amazing," the 33-year-old said.

"My training in Chile has been going really well and I’m constantly improving my technique."

Abarza suffers from Charcot-Marie-Tooth disease, a hereditary neuropathy which causes the progressive loss of muscle tissue in various parts of the body.

This has not stopped his progress in the pool, however, as he seemingly continues to improve with each passing year.

"Now I’m going to prepare myself for next year's Parapan American Games in Lima and then, God willing, the [2020] Paralympics in Tokyo," he added.

Also performing strongly today was S9 world champion Daniela Giménez with the Argentinean taking gold in the women’s 200m medley and silver in the 50m freestyle.

Brazil’s Camille Rodrigues added a silver medal in the women’s 100m S9 backstroke to her 400m freestyle bronze from yesterday.

Action in São Paulo is due to conclude tomorrow with the 50m and 100m breaststroke, and 100m freestyle events.

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.

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.