Occurring only in the Ocean biome, Islands are Named Locations which consist of a large island above the surface of the ocean. They follow the naming convention "<NAME> Island". Named islands function as dungeons and have rulers and large numbers of hostile NPCs
Islands are simmilar to their randomly generated counterparts Small Islands, and are functionally identical to small Grasslands or Jungle biomes, spawning the same mobs and containing the same landscape features. Islands can spawn world bosses.
You can find islands easily using the grid system trick, because they are generated like dungeon on land.