Let me start off by saying this is the first cake (and first post!) I have ever made, so it has many flaws!! The octopus was a Styrofoam ball covered in tinfoil then marshmallow fondant. The tentacles are marshmallow fondant. I used three cakes and kind of tapered them off to look like a rock (didn't work so well, oh well!).. The "sand" is brown sugar and the seaweed is colored white chocolate.