A wooden twig

 As Rock stood in line at an apparently immensely popular buffet, a pleasant but not particularly pretty nurse struck up a conversation. Shortly after it began, she said, "Hold still for a minute. You have something in your left ear." Rock paused as the nurse extracted the thing she had noticed. When she showed it to him, he was stunned. It was a wooden twig, perhaps three inches long with multiple tiny branches. Before he said anything to the nurse, the twig quickly blossomed into an ornate white flower. Moments later, with no further thought, Rock swam back to his car in an uphill swimming pool, twenty feet wide and a quarter-mile long. Gravity did not affect the water, which did not seem odd to Rock.