Open Water City-States

Wired reports on "a small team of Silicon Valley millionaires" who hope to develop "a new option for global citizenship: A permanent, quasi-sovereign nation floating in international waters."
They call this practice seasteading.

The seasteaders want to build their first prototype for a few million dollars, by scaling down and modifying an existing off-shore oil rig design known as a "spar platform." In essence, the seastead would consist of a reinforced concrete tube with external ballasts at the bottom that could be filled with air or water to raise or lower the living platform on top. The spar design helps offshore platforms better withstand the onslaught of powerful ocean waves by minimizing the amount of structure that is exposed to their energy.

Build enough of these spar platforms and you've got yourself a "deep-water city-state."

They touch on the political and economic circumstances involved in steading the high seas, including SOLAS, the International Convention for the Safety of Life at Sea, and UNLOS, the United Nations Law of the Sea. They mention the process of buying a Flag of Convenience, in which hopeful microsovereigns can "shop around for a country that has the least objectionable laws and rates, and count on the seller’s apathy to minimize restrictions. A seastead is potentially high-profile, and if it proves a serious embarrassment to a registrar it may lose its flag."
The seastead's power storage needs are then discussed in terms of electrochemical batteries, gravity batteries, and supercapacitors, and the production of this power will, the authors presume, come from wind and solar systems, and even one or two fuel-powered generators. Of course, there's also the power of the sea to consider – and the authors' "favorite" method for harvesting "wave power" is something called Isaac's Wave Pump. This project has become more than a concept and is rapidly moving towards realization. This is the new age "life at sea". I love this idea, and hope to see it come to fruition. Below is a simplified diagram of the operation.