This book is the outcome of my analysis of all available knowledge of the Southeast Asian Waters. It is hoped that workers in the region, whether in oceanography or other branches of science may find it a source of information and a stimulus to undertake further research in these waters. Some chapters in this book are summaries and condensations of already known facts, but others offer new ideas and interpretations, particularly those chapters on monsoon circulations and their dynamics, on deep circulation and its relation to surface circulation, on the energy exchange between sea and atmosphere, and on the quantitative description of the exchange of water in the deep sea basins.