Book excerpt: This title brings to light the discoveries and insights into the lives of many marine species made possible over the last decade by passive acoustic recorders (PAR). Pop-ups, ARF, HARP, EAR, Bprobe, C-POD Atag, and Dtag are the acronyms of some of the many PARs that have changed our understanding of how marine animals live and strive in the ocean. Various types of PARs are used by different investigators in different areas of the world. These recorders have accumulated copious amounts of very important data, unveiling previously unknown information about large marine animals. Temporal, seasonal and spatial distribution patterns have been uncovered for many marine species. There have been many discoveries, new understandings and insights into how these animals live in and utilize the ocean and the importance of acoustics in their lives. Listening Within the Ocean summarizes these important discoveries, providing both a valuable resource for researchers and enjoyable reading for non-professionals interested in marine life.