That is extremely cool. In one of my Jacques Cousteau books, he talks of exploring the dark ocean floor in one of their deep sea submersibles. He sees something square, a shape that doesn't occur in nature, and has Phillippe drive over for a closer look. Turns out this little octopus had gone way over there (several hundred yards), to fetch these small white stones, and brought them back to make a little square fence around his octopus hole.
As they drove around some more, it turned out that every one of those kind of octupuses had done the same thing. In the dark. Which means that right now, down on the deep ocean floor somewhere, there's a little octopus going, "Say Bill, love what you've done with the place - where'd you get them anyway?"