PBS | 9:00 pm

With the "Sharknado" TV movies having done big business, there’s increased awareness of — and interest in — what the title of this episode spells out: "Why Sharks Attack." Of course, the program takes a much more serious approach to the subject, with American and Australian shark experts taking scientific views of what provokes the so-called "eating machines." There’s an urgency for answers as shark populations increase in some areas.