Stroke of luck

Jeff ran down the hall to the pool. He could hear the sound of someone in the water. He had found her. "Jan" he called, but she kept on swimming, like a machine. Down to the far end of the pool. Then back up. On and on she swam, not hearing his voice, not missing a stroke. She must be all right, Jeff thought. Then he saw that Jan was having trouble. She wasn't swimming straight. She was moving across the lane and buming into the rope.