NASA trains astronauts for spacewalks in giant pools

Before you get to float in the vast emptiness of the cosmos, you have to practice in the ultimate deep end. Because true zero-gravity is impossible to sustain for long periods on Earth, aerospace engineers rely on neutral buoyancy to mimic the sensation. Trainees spend hours submerged in giant, heavily supervised pools, painstakingly rehearsing every bolt turn and wrench maneuver they will need to execute in orbit.