Synthetic Aperture Radar (SAR), an important earth observation sensor, has been used
in a wide range of applications for land and marine surveillance. Polarimetric SAR
(PolSAR) can obtain abundant scattering information of a target to improve the ability
of target detection, classification, and quantitative inversion. In this paper, the
important role of PolSAR in ocean monitoring is discussed with factors such as sea
ice, ships, oil spill, waves, internal waves, and seabed topography. Moreover, the
future development direction of PolSAR is put forward to get an inspiration for further
research of PolSAR in marine surveillance applications.