The characteristics of the different parts of the ocean vary depending on the region. While the coastal ocean changes rapidly and presents the largest amount of biological activity, it also shows the largest exchanges with the continents through the estuaries. Meanwhile, the open ocean extends much deeper and includes relatively strong surface currents and a much slower circulation in the deep ocean.

This Reading elaborates on the concepts presented in the Activities: Water: The Sum of Its Parts; The Ocean; The Tides: A Balance of Forces; Waves; and The Ocean: A Global View from Project Earth Science: Physical Oceanography, Revised 2nd Edition. Although the Reading was written especially for this volume with the teacher in mind, students should also be encouraged to read them for both interest and additional study.