As astronauts train for space voyages, they use the Neutral Buoyancy Space Simulator, which is effectively a very large, very fancy swimming pool with a bunch of equipment in it. The water simulates the effect of weightlessness in space, allowing astronauts to rehearse tasks that they'll have to do while in space.
In this NPR video, we see an early look at the NBSS, set to ambient music. As Atlantis astronauts start their final spacewalk this morning, sit back and witness some soothing, Seventies-style history:
If that's not enough shuttle action for you, check out this "Shuttle Through the Decades" video: