BUILD AN ICE RAFT. SAVE THE BEAR. DON'T FREEZE. The Arctic ice is melting, and Nanuk the Polar Bear is in big trouble. He's stranded, starving, and staring down a deadly 175km swim across the open ocean. Leo and Lily have a plan-but it's crazy. They aren't just watching from the sidelines. Using their high-tech drone and a secret substance called Pykrete (super-strong ice made with wood pulp!), the Nature Hackers are on a mission to 3D-print a floating life raft right under the bear's paws.