This book provides up-to-date information as well as introduction to underwater acoustics, which is described as the analysis of the propagation of sound in water and the interplay of the mechanical waves that constitute sound with the water and its boundaries. A wide range of topics are encompassed in this book like localization of buried objects in sediment with the help of high resolution array processing techniques, underwater acoustic source localization, adaptive strategy for underwater acoustic communication, etc. Researchers and scientists from across the world have contributed valuable data and information in this all-inclusive book. The aim of this elucidative book is to serve as a useful source of reference for readers including researchers, students and even scientists who are interested in acquiring knowledge regarding this field.