What do astronauts do for fun? They make music videos, they cook, they garden, and they also play games. Like ping pong. With water. Because why not?

Astronaut Scott Kelly is spending a year in space aboard the International Space Station. He has two hydrophobic ping-pong paddles that cause the ball of water to bounce right off of them. It looks like fun, but it’s also interesting science.

Hydrophobic materials like this one are of interest to scientists because not allowing water to stick on a surface means that that surfaces can be kept cleaner–a valuable trait in places like hospitals, which are constantly trying to keep infections at bay.

Watch Kelly’s video in the tweet above.