In the first live 4k video stream from the International Space Station on Wednesday (April 26), NASA astronauts Peggy Whitson and Jack Fischer wowed viewers by playing with water in zero-G and in ultra-HD.

The duo started off with a game of "space ping-pong," as Whitson called it, using a weightless wad of liquid water instead of a traditional ping-pong ball. As Whitson and Fischer batted the water around with their paddles, smaller blobs of water broke free from the original ball, making the game a little trickier. The ping-pong match ended with Fischer slurping up the floating liquid. [In Photos: Expedition 51 Mission to the Space Station]

Then they spiced up their water play by adding Alka-Seltzer and food coloring to their weightless water blobs. "A lot of these are things we do to have a little bit of fun just because you can do them in zero gravity," Whitson said during the live stream.

Whitson and Fischer are not the first astronauts to play ping-pong at the space station, but they are the first to do it during a live 4k video stream. In 2016, NASA released a video of astronaut Scott Kelly playing a solo game of zero-G ping-pong at the orbiting laboratory.

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.