Im sorry all my pic's are in storage on my other computer right now as I am in the process of selling my house. Try to visualize a potted calla in a plastic pot inside a clay or ceramic pot of similar size (with drainage holes) Place potted plant in bank areas where the water is only an inch or two and gets some sun. Weight down if necessary with pebbles/small rocks.
I think Callas would do good here in the pond too. We have ours (monstrous) on the North side of the house and is quite swampy in the winter and spring, so their "feet" are always wet. I think maybe if they were planted right at the edge, maybe in 2" deep water when my pond is at it's maximum, would be a good location. If I have success, I will post. Also, our little frogs love calla lilies--they hide inside the blooms and take care of bugs.