He did last year, alongside mayor Hidalgo and others, such as Tony Estanguet, who is a former athlete and was overseeing the olympics and the minister for sports.
Amusingly, President Macron also said that he was going to swim in it to prove it was safe, but ultimately didn't. According to Wikipedia, "the primary reason cited was the concurrent French general election, but reports also circulated that protestors had planned a mass defecation event to coincide with the swim."
