Japan's Horigome Yuto has won gold in the first-ever Olympic skateboarding event.

The 22-year-old got off to a slow start in the men's street competition, finishing sixth in the qualifying heat. But he was at his best in the final, where he landed four out of five tricks to rack up the highest overall score.

Horigome said afterwards that he felt he had nothing to lose and skated as aggressively as possible.

The Tokyo native beat a crowded field that included American star Nyjah Huston. The gold medal favorite fell repeatedly in the final and finished seventh.

Another sport made its Olympic debut on Sunday. Qualifying heats for the men's and women's surfing competitions were held in Chiba Prefecture, east of Tokyo.

Meanwhile in swimming, Japan's Ohashi Yui won gold in the women's 400-meter individual medley. The 25-year-old has recently struggled with injuries and illness. But she cruised to victory on Sunday, finishing over half a second ahead of her closest rival.

Ohashi said afterwards that she never imagined she would be standing on the podium, and thanked her teammates for their support.

Chase Kalisz of the US won gold in the men's side of the competition. He took silver in the same event in Rio, but went one better this time around. It's the first gold for the US in Tokyo.

In the women's 400-meter freestyle relay, Australia set a world record as it won gold. Canada took the silver, while the US finished with the bronze.