I’m continually astounded by this new Blue Planet II series: Quite often, I can’t believe what I’m seeing. And afterward, with the little how-they-filmed-it bonuses at the end of each episode, I can’t believe how they captured what I can’t believe I’m seeing. Tonight, for example, in the vibrantly colored installment called “Coral Reefs,” you can watch an octopus that’s so ingenious that he hides himself from a predatory shark by curling into a ball on the sea floor, while using all eight tentacles to quickly pull shells and shell fragments around him as an instant disguise. Can you see the octopus in this picture?