Command of the sea Great Britain accepted the principle in 1805; Russia, in 1824; and the United States (tacitly) in 1894. Many treaties, including the Treaty of Versailles, have dealt with the open seas, and currently the United Nations Convention on the Law of the Sea formalizes this freedom. Historically, many powers attempted to extend command of the sea into peacetime, imposing taxes or other restrictions on shipping using areas of open sea. For example, Venice claimed the Adriatic, and exacted a heavy toll from vessels navigating its northern waters. Genoa and France each claimed portions of the western Mediterranean. Denmark and Sweden claimed
Gulf of Bothnia a number of rivers from both sides; consequently, a salinity gradient exists from north to south. In the south the water is the normal brackish water of the Baltic Sea, but in the north, in the Bothnian Bay, the salinity is so low, from 0.4% near Kvarken to 0.2% in the northernmost part, that many freshwater fish such as the pike, whitefish and perch thrive in it. Being nearly fresh, the gulf is frozen over five months every year. The icing of the Baltic Sea begins and ends in the northern Gulf of Bothnia. Traffic restrictions for icebreaker assistance are