get yourself some black plastic oil pans and plant them in them with clay garden soil. Put gravel on the top and then sink into the pond.

Ok, I did this last night. I cut open the bags and there was a tiny root looking thingy that I planted in the clay and oil pan. Didn't look like much...are they seeds or tubers?..

They're tubers. In a warm pond, it won't take long for them to sprout and start sending up pads.