Wikipedia has one. There is a lot of it https://commons.wikimedia.org/wiki/File:International_waters... (it is the dark blue)
Indeed, but most of it is very deep and won't be seeing any new islands soon.
Also see wikipedia "principality of sealand". Some british nut tested a lot of the legal precedents. Short version, it totally works, although there was that one time his nation was conquered by mercenaries hired by a german lawyer, and his son was taken hostage. So, self defense is a very real concern.
Given that, there is no benefit to leaving exclusion zone. You can just set up in international waters much closer to shore.