An almost obligatory feature of Floating Continents, Floating Castles, and Flat Worlds, (especially if the setting is Crystal Spires and Togas) is waterfalls off the side of the structure. Awesome but Impractical in the case of smaller floating islands since you'd expect the water to run out fairly quickly since they don't have a very large area of land from which to collect rainfall. It's especially strange in the case of Flat Worlds since it doesn't seem that there would be anything to bring the water back. Examples of Waterfall Into the Abyss include: