Members of the NEEMO 19 crew participate in an underwater excursion outside the Aquarius habitat. ESA astronaut Andreas Mogensen (in the foreground) and ESA astronaut trainer Hervé Stevenin are part of the four-strong crew. NEEMO – NASA Extreme Environment Mission Operations – trains astronauts for life in space. Living and working in an underwater base is similar to being on a space station. NEEMO’s underwater habitat off Florida acts as makeshift a space base for astronauts to make regular ‘waterwalks’ in full scuba gear. Both underwater missions plan sorties for the astronauts to simulate spacewalks.