If your pond is already filled with water, this is not going to be an easy task as you will need to bring in a large amount of landfill (dirt) to build up the island. However, if you bring in any dirt, you may risk the possibility of stirring up or introducing harmful toxins into the lake which can kill the swans. The best idea would be to see if the swans will use a nesting box which can be anchored into the lake. Knox Swans in Indiana sells the nesting boxes. We have heard various reports on the successes and failures of the boxes, but at least you are not causing a poisoning situation at your pond. The Regal Swan.