European Space Agency astronaut Alexander Gerst, Expedition 40/41 flight engineer, attired in a training version of his Extravehicular Mobility Unit (EMU) spacesuit, is about to be submerged in the waters of the Neutral Buoyancy Laboratory (NBL) near NASA's Johnson Space Center, 17 September 2013.
Divers (out of frame) are in the water to assist Gerst in his rehearsal, which is intended to help prepare him for possible work on the exterior of the International Space Station.