The few years that I have been using foam in a pond setting has been more work than it's worth. Muskrats seem to chew on it for fun, and build tunnels in it here in Wisconsin. Chasing the pieces around when you move the dock isn't fun. We tried some empty 55 gallon plastic drums or smaller 35 gallon ones. I would think that a few phone calls could find some cheap or free. They could be strapped in, and a frame could be built around them.
Robert B
