Since recently in real life there was a planet discovered close to it's star but with a high gravity. It's water is so densely packed that it turns to ice. And since it's close to the star this ice is hot. If something like this is possible then there could possibly be worlds either due to low gravity, magnetic properties in mineral ore, or tough gravitational pull from another planet(if your homeworld is a moon) that would result in Giant possibly mountian sized islands floating in the air. Similar to the movie avatar and the recent film interstellar. Island dwarfism and gigantism might play a role but unlikely.