Almost all times of the year, Manzanillo's shallow reefs and shores are teeming with octopus. Though well camouflaged, with a little practice (or an experienced guide) you can pick one out. For protection, they pick up empty shells and rocks, and use the suction cups on their tentacles to draw them around their bodies to form a hard barrier. You can recognize the den of an octopus because of the array of small clam and mussel shells around its entrance. Small bivalves are a favorite food of our 8-armed friend. On the second day of filming, the Discovery crew was lucky to find an unusual event--an octopus killing a porcupine puffer.