Abstract: Underwater acoustics plays a significant role in safeguarding national maritime security and promoting the exploration and development of marine resources. This paper begins by tracing the progression of underwater acoustics research from domestic and global perspectives, followed by a comprehensive overview of several key areas within the field. These includes underwater acoustic equipment, underwater sound propagation, ocean ambient noise, underwater target detection, identification and tracking techniques, target bearing estimation and localization methods including both physical-feature-based and multi-array-based passive/active methods. Considering the challenges encountered in practical applications, the paper discusses the development trends of underwater acoustic equipment and critical technologies. This aims to provide insights for advancing fundamental theories and applied research in underwater acoustics in China.