The duo took part in a bizarre exhibition match on the court which had been laid in the water of Doha Bay, Qatar, to promote the upcoming ATP World Tour.
And though the pair have the experience of winning 25 Grand Slam titles between them, neither had played on a surface anything like this before.
While we don't know what score the game ended at, it's not our main concern, we want to know what happened to the ball boys… or should that be ball buoys.
Federer added, "It was good fun. It was so different. You’re always excited and nervous to see how it will turn out. It is always nice promoting an event and an entire tour with Rafa."