The following link directs to an interesting Movie about the first
offshore drilling platform, which became an autarkic city, in 1949.
This shows, that the idea about a "Floating-Permaculture" is not
as futuristic as it sounds.

OIL ROCKS - City above the Sea
Original title: La Cité du Pétrole
Director: Marc Wolfensberger
Camera: Jon Björgvinsson
Sound: Blaise Gabioud
Editing: Patrick Léger, Peter Entell, Ana Acosta