The mixed layer and upper ocean are a region of immense interest to physical oceanographers, meteorologists, and climate scientists because this is the boundary through which energy, momentum, buoyancy, and gasses are exchanged between the ocean and the atmosphere. The upper ocean is also a rich ecosystem for a vast array of ocean organisms and marine wildlife as well as a region of great Naval tactical importance. Given these factors, it is rather surprising that ocean acoustics has paid little attention to this significant region, aside from very high-frequency studies of bubble properties and gas entrainment. From the standpoint of transmission loss, the major work on the problem seems to go back to the Acoustic, Meteorological, Oceanographic Survey (AMOS) of the mid-50s. Here, a review is presented of relevant ocean processes that may be important for acoustic propagation at frequencies ranging from several hundreds of hertz to several kilohertz, where the foundation of the analysis is normal mode and transport theory. Processes of interest are surface gravity waves including subsurface currents, internal waves and tides, wind driven inertial oscillations and Langmuir circulations, eddies and submesoscale processes, turbulence and spice, bubbles, and fishes.