Although the typical depth of oceanic basins is 5 km, a significant fraction of the earth's surface is covered by a much shallower sheet of water (only about 100 m in depth). In addition to many small lakes and lagoons, this includes extensive areas, with horizontal dimensions of 100 km and more, such as the Great Lakes, continental shelves, or large gulfs such as the Gulf of Maine or the North Sea. These relatively large bodies of water behave dynamically in an ‘oceanic’ manner, in the sense that motions in them are strongly affected by the earth's rotation. They will be taken to constitute the ‘coastal ocean,’ a term that covers enclosed and semienclosed basins, as well as open seas such as the broad and flat continental shelves of the ‘Atlantic’ type or the narrow and steep shelves of the ‘Pacific’ type.