Speciale maintained a healthy lead in the final race to top the 23-strong fleet at Club Nautico San Isidro to claim gold in the women’s Windsurfer - Techno 293+ event.
Russia's Yana Reznikova, 15, clinched bronze after overtaking Israel’s Naama Gazit on the leaderboard.
Earlier, Renna had finished second behind Greece’s Alexandros Kalpogiannakis in the men’s category.
“It was a perfect race,” said Speciale. “I had an easy start and I pumped a lot. Two medals for Italy is amazing,” Speciale said, who admitted to feeling anxious about her position on top of the leaderboard coming into Friday’s race. “I was so nervous but when I went into the water I started to concentrate on the race and then I was calm,” she said.
“We’re like brother and sister,” Speciale continued of teammate and roommate Renna. She also admitted that the duo, who live and train in Ancona, had kept each other focused and motivated ahead of these Youth Olympic Games.
“Every morning we told each other we had to train to the max because the Youth Olympic Games are once in a lifetime. We pushed hard every day.”
Kalpogiannakis, 16, topped his fleet despite being overtaken by his opponents and finishing seventh in the final race. “The conditions were very difficult because there was a current and shifting winds. It wasn’t so easy,” he said.
The men’s Bronze went to 15-year-old Finn Hawkins, who overcame a tricky start to finish third in Friday’s race and clinch Great Britain’s first medal in Buenos Aires. “It’s great to be the first,” Hawkins enthused.