|This is one of the EVA (spacewalk) training modules in the Russian Hydrolab. It is a mockup of the Russian docking module called 'Pirs' or CO1, used as an airlock as well as a docking port for the ISS. In this tank, divers help the cosmonauts to train for their spacewalks. Underwater training simulates some aspects of the weightlessness they encounter during the EVA. A single spacewalk can last for seven hours without a break, so the cosmonauts have to be both fit and strong.