During WWII, Great Britain constructed several floating 'forts' a few miles outside its territorial waters to prevent the Nazis from mining its shipping lanes. The forts consisted of a pontoon base, with two hollow towers rising from the base, holding up a deck. by 1956, the structures were abandoned.
In 1967, a guy by the name of Major Paddy Roy Bates, a British pirate radio broadcaster, and his family, occupied the abandoned platform. He declared the platform the 'Principality of Sealand', with him as the head of state.
A year later, when a group of British workmen approached the fort to service a buoy, Michael Bates, the 'Crown Prince' chased them off with gunfire. In the subsequent court case, the British legal system ruled that as the fort lay outside the 3 mile British territorial waters, they had no jurisdiction over the fort and dropped the case. By 1975, Sealand had a constitution, an anthem, a currency and passports.
But wait, the story gets weirder. In 1978, while the 'Prince' and 'Princess' were visiting Austria, Sealand was attacked by some German dude named Alexander Achenbach, who declared himself the 'Prime Minister of Sealand'. Achenbach and a group of German and Dutch mercenaries attacked the platform, taking the 'Crown Prince' hostage. However, upon return from Austria, the elder Bates managed to turn the tables. He re-captured his platform, freed his son, and in turn took Achenbach and his band hostage. They were charged with 'treason' and a ransom was levied against them.
Various European governments petitioned Britain to intercede, but the Brits refused, citing lack of jurisdiction. Finally, Germany wound up sending a diplomat to Sealand and negotiating Achenbach's release. Upon regaining his freedom, Achenbach set up a 'government in exile' in Germany.
I have to say, this is one of the weirder stories I've come across in my life... I don't even know what to say about it, other than - I need to find a platform somewhere in the Carribean and declare myself His Serene and Most Excellent Highness Prince E-Kvetcher the First.