On Monday, Vaast won men's surfing gold on his Tahitian home waves at Teahupo'o, becoming the first Olympic champion from the French Pacific island.
He wowed supporters again on Friday as he surfed along France's iconic river nearly 16,000 kilometres (9,950 miles) from his native Tahiti.
The 22-year-old trailed behind a boat, using the small wave it created as it sped along the Seine, with the Eiffel Tower in the background.
The beaming athlete proudly showed off his gold medal as he rode the Paris waves.
He said surfing down the Seine was a once-in-a-lifetime experience, even if the waves were much smaller than he would find in Tahiti.
"Surfing in the Seine is great, it's mega, but doing it with the Eiffel Tower behind you is even more special," he said.
Supporters including French Sports Minister Amelie Oudea-Castera showed up to cheer on the champion.
Vaast, who first stood on a surfboard aged four, rides much bigger waves in Tahiti, an island on the Pacific archipelago of French Polynesia, a French overseas territory.
He said surfing behind a boat was a different experience but it was still a "unique moment."
"It's still a wave, it's still gliding and I'm happy to have been able to do that at least once in my life," he said.
Tahiti hosted a spectacular Olympic surfing competition on the Teahupo'o waves that often reach two to three metres and sometimes a lot higher.
Vaast has said a supernatural force in Polynesian culture known as "mana" helped him win.
