Undersea acoustic applications to detect, communicate, navigate, monitor and measure within the ocean, are dependent upon a good physical understanding of sound production, propagation, and scattering in the ocean environment. This proceedings volume provides interesting new research results in ocean acoustics and includes two-to-three decade reviews of progress in different topics in ocean acoustics, including computational acoustics, shallow-water acoustics, seafloor and sediment acoustics, boundary scattering and reverberation, ocean ambient noise, geoacoustic inversion, marine bioacoustics, arctic acoustics, signal processing, underwater acoustic communication, and underwater sound projectors.