How deep is the water? Can you dig back into the earth in 2 or 3 places around the island to create a more gradual slope from the edge inwards? At the same time you could create a beach area, if the surrounding water is not too deep.
Are there any flowers, reeds and so on, or is it just plain grass? It certainly looks a bit barren at the mo. Ducks like water plants so maybe plant some of them into the water at the island edges, with rushes and reeds for cover.