Blake Lively stars as Nancy, former medical school student from Galveston, TX, who travels to her recently deceased mother's favorite secret surfing spot in a lush spot on the Mexican coast to feel a connection with her as part of the grieving and healing process. When her friend bails on her at the last minute, she decides to go it alone, catching some hellacious waves and enjoying the brisk sunny air. However, she isn't really ever alone, as she soon encounters a massive great white shark when she inadvertently enters his feeding zone in shallow waters off the coast, and Nancy is the intended next course on its menu. With no easy way back to shore, it's a cat-and-mouse game of survival between woman and shark to see which one will ultimately prevail.