The Associated Press reported that about 400 anti-capitalist protestors gathered to block roads in the town in southwest France. The crowd was largely peaceful, though some demonstrators threw rocks at police.
Police responded with warning shots and then used the water cannon and tear gas, according to the AP.
Thousands of protestors marched peacefully from the same area to the Spanish border earlier Saturday to demand further action against climate change and economic inequality.
President Trump is in Biarritz, France, for the annual meeting with the six other world leaders of the G-7. The event often attracts protesters who come to demonstrate on an array of topics.