A major task for physical oceanographers is to determine the movement of oceanic water from observations. This book introduces a simple, efficient inverse method, the P-vector method, with a two-step determination of the velocity from hydrographic data. The book provide insights into the basics of the P-vector inverse method and the features of the inverted global and regional ocean circulations. Upper undergraduate and graduate students as well as oceanographers, marine biologists and other environmental scientists will find this book of great value as a tool for their continuing studies.