The octopus sign looks like an octopus swimming around in the water. You start by placing the finger of your non-dominant hand on top of the wrist of your dominant hand, to make the head of the octopus. The fingers of your dominant hand become the tentacles of the octopus. Then move your hands around and move your "tentacle fingers" as if the octopus was swimming.
Octopus is one of the more advanced signs, but also one of the most fun for infants to do. They love to make their octopus skulk around, ready to surprise the unwary!
We use octopus to encourage a richer vocabulary when visiting the beach or the aquarium.