The Space Swimmers — Gordon R. Dickson

Patrick Joya lifted his head to scan the southern sky and saw a dark bluish shape flicker against the clouds. Growing larger and larger the object undulated like a wide piece of cloth carried along on a moving current of water. "He could hear the babble of voices around him swelling to a mounting groan of panic. The sound went racing like a cresting wave back toward the Terminal where the thousands there would be lifting their gaze skyward. "Another Space Swimmer, Pat thought with sinking heart. It seemed as if it intended to swallow up the sky - for the brightness of day had blackened into night . . . .accepted their robot-like existence. Either way, the human race was doomed!