ESA astronauts Andreas Mogensen and Thomas Pesquet returned from their “Seatest” experience at NASA’s underwater test bed in Florida. Mogensen stayed 20 m underwater for four nights with three other astronauts in training, or AIT’s, as I call them. The AITs performed “waterwalks” to simulate “spacewalks” and practiced crew procedures on the underwater space station as if it were the International Space Station. They re-created lunar spacewalks by changing the weights on their scuba gear. The simulation also involved a test of the new “gymnasium-in-a-box” meant to keep astronauts fit during space travel. Pesquet stayed above the water (or on the ground) to serve as light director and communicator.