The book is the first to focus on the physical oceanography of the North Indian Ocean (NIO), a special region of the global ocean that exhibits a distinct seasonality due to the impact of the South Asian Monsoon (SAM). It is written as a textbook about the NIO for graduate students, lecturers, and researchers in physical oceanography. It will also be useful for courses on the interior, coastal, and equatorial dynamics in any other ocean. It helps readers, particularly new entrants to the field, to gain a comprehensive understanding of tropical-ocean dynamics by: developing from first principles the equation set for the linear continuously stratified (LCS) model, which has long been used to study tropical oceans; and then obtaining solutions that explore different aspects of the dynamics.