Perhaps. If it had any citizens.
5) Has a transportation system for moving goods and people.
No.
6) Has a government which provides public services and police power.
Yes, but that police power is certainly not absolute. The United Kingdom can assert its authority over Sealand quite easily with a few police officers.
7) Has sovereignty. No other State should have power over the State's territory.
No. The United Kingdom has power over The Principality of Sealand's territory. The British government was quoted in Wired, "Although Mr. Bates styles the platform as the Principality of Sealand, the U.K. government does not regard Sealand as a state."
8) Has external recognition. A State has been "voted into the club" by other States.
No. No other country recognizes The Principality of Sealand. An official from the United States Department of State was quoted in Wired, "There are no independent principalities in the North Sea. As far as we are concerned, they are just Crown dependencies of Britain."
The British Home Office was quoted by the BBC that the United Kingdom does not recognize Sealand and, "We've no reason to believe that anyone else recognises it either."
So, The Principality of Sealand fails on six of eight requirements to be considered an independent country and on the other two requirements, they're qualified affirmatives. Therefore, I think we can safely say that the Principality of Sealand is no more a country than my own backyard.
