This chapter talks about the main oceanic phenomena and hydrodynamic factors, which are responsible for the formation and variations of microwave remotely sensed data. The emphasis is to specify processes and events that are potentially observable by passive (and active) microwave sensors. The structure of the ocean–atmosphere interface can be divided into three categories: the near-surface upper ocean layer, the interface itself, and atmospheric boundary layer. The upper ocean layer is characterized by thermohaline finestructure, double-diffusive convection, circulations, internal wave motions, and turbulence. The near-surface atmospheric boundary layer is characterized by turbulent fluxes, stratification, and stability. Ocean surface waves are strongly diversified by geometrical form and space–time scales. The weak turbulence theory is based on the solution of the kinetic equation for a spatial wave spectrum or the spectral density of the wave action.