I like it also. When I had my pond constructed, I asked the builder to deposit some of the larger specimens dug out of the hole up above the water line for sitting and fishing from. He found some really large ones and set them up high and in some nice spots.

A few weeks after the pond started filling, as heavy as they were, they started sliding down the mud into the basin like they were on sleds. I started with about 6 large 400lb+ boulders, now there are only two above the water line and they are sitting on-edge so they are useless. Two of the largest made it all the way to the bottom of the pond. At least they stopped moving... for now.

Lesson is: Anchor the darned things to some really solid earth with long, pounded-in metal post/spikes or something.