Most of the earth is covered with water, so eventually we will need to colonize the oceans in order to survive. At least that's what arch villain Karl Stromberg told James Bond when he had him trapped on his ocean lair Atlantis in the Bond thriller The Spy Who Loved Me.
While I don't think the folks from Zigloo have an evil plot like Stromberg's to destroy the land based world, it is striking how much their ocean habitat Gyre resembles Stromberg's Atlantis. But instead of a base for hatching evil plots, this huge floating city is intended to be a center for both eco-tourists and scientists alike, combining a host of green technologies to remain self-sufficient.
With space equivalent to about 40 football fields to support as many as 2000 inhabitants, Gyre will be a truly complete community with shops, restaurants, hotels, and recreation areas. Power will come from a combination of solar, tidal, and wind, while the wind generators can also be used as propulsion devices to move the entire structure. Rainwater will be collected and purified on board, and even though there's no mention of food sources in the proposal, I'm guessing that you had better like fish.
While no actual construction plans are mentioned, Gyre does at least look a little more feasible than that Lilypad city concept.