WARNING - Lots of theoretical rambling ahead - You have been warned.
I wonder what the rules are for things like abandoned barges and such? Can you just wander off with a few if nobody else claims them??
I wonder how pissed the authorities would get about having a bunch of barges attached together wandering about the ocean? Then there's questions such as stability, power sources, how to get bandwidth that doesn't suck, stuff like that. And what flag to use. I know you need a flag frome /some/ country, otherwise they call you a pirate and shoot at you, which would suck. I can think of one micronation that might be a good choice, although I'd need to look into it a bit more... Probably just use US currency, it's common, and supposedly equivalent to the currency of previously-mentioned micronation.
Maybe satelites would work for a web connection best? Of course, satelites need somewhere to connect to that has a stationary uplink. I don't know if they have any satelites, but the main business in aforementioned micronation claims to have a direct connection to the internet backbone. (I have no clue what "STM-1 to STM-16 and higher" means though).