Patricia Shaver, age 13, of Columbus, Ohio, for her question:

HOW ARE TERRITORIAL WATERS MEASURED?    

Territorial waters are areas of the ocean where a nation has sovereign rights. These rights include control of fishing, navigation and shipping, as well as the use of the ocean's natural resources. There is no standard method used by nations to measure their territorial waters.

Various nations have set different outer limits for their territorial sea. Most of the approximately 120 coastal nations have a limit of 12 or fewer nautical miles.

The United States has a limit of three nautical miles. A few nations claim a limit of as much as 200 nautical miles.

Many countries prohibit foreigners from fishing in their territorial sea.

Many disagreements between governments have occurred about the extent and use of territorial waters. The United Nations has sponsored a number of conferences to draw up an international treaty governing the use of all the world's oceans.