Pond Boss Forums POND CONSTRUCTION Creating habitat store bought poly structure

I was at a zoo this weekend and in a polar bear habitat there were some poly propylene plastic structures which looked like hexagonal shapes about the size of 5 gallon pails. They were all made fused together in a structure about the size of a refrigerator. I asked the guide about them and he said they throw anything unusual in there to entertain the bears, as long as they can't hurt themselves with it. From the looks of this thing it would be excellent structure and easily be weighted down and sunk. Does anyone know if there is a type of manufactured structure type arrangements sold and who sells them?