Yes and no... from what i have seen i use world pregen viewer and it will have all the structures sometimes the latest version feels like a 50\50 chance for the sunken sea to spawn in the underground desert and sometimes im not too sure where to find the shimmer although that is still new to me and im not sure of its spawn locale...also it may be a world pregen viewer thing but it takes FOREVER to load a world sometimes it gets stuck so i have to reset my tmodloader and redo it... again may be the pregen viewer