Coastal discharge plumes are often visible on satellite imagery acquired by optical, infrared, and microwave sensors, because they may change the local chlorophyll content, the sea surface temperature (SST), or carry surface-active substances, like hydrocarbons. In this paper, we give an overview of different kinds of discharge plumes and demonstrate the ability of satellite-borne sensors to monitor them. The chosen examples are a river runoff in northeastern Spain, a municipal waste plume in southern Italy, and an industrial waste (cooling) water plume in northeastern Spain. We demonstrate that the combination of satellite data from different sensors (data fusion) may help to better interpret the observed features and to specify the impact of coastal runoff on the local ecosystem. Finally, we summarize results from a comprehensive statistical analysis of marine oil pollution using more than 700 radar images of European marginal waters.