I've been watching the activities of the
SeaSteading Institute for some years, and it still seems that they are no closer to starting new countries on floating islands than they were a decade ago.
Well, a Korean company has successfully launched a series of much small floating islands, that will float in the Han River in Seoul.
From the
Sydney Morning Herald:

Along with two other artificial islets, Vista and Tera, to be launched by the end of April, the cluster of man-made floating islets will be used for conventions, water sports, restaurants, performances and exhibitions.