Whatever roi g answered is right !! :D In simple, High Sea is a term of international and maritime law; the open ocean, not part of the exclusive economic zone, territorial sea or internal waters of any state.

In maritime law, the waters lying outside the territorial waters of any and all states. In the Middle Ages, a number of maritime states asserted sovereignty over large portions of the high seas. The doctrine that the high seas in time of peace are open to all nations was first proposed by Hugo Grotius (1609), but it did not become an accepted principle of international law until the 19th century. Activities permitted on the high seas include navigation, fishing, the laying of submarine cables and pipelines, and overflight of aircraft. cowboy...

The 'High Seas' is an older term for oceans or bodies of water that don't belong to a country, the term 'international waters' is more common now. http://en.wikipedia.org/wiki/International_waters