This Pilot Study aimed at improving the information on the state of the Indonesian marine environment that is gained from satellite data. More than 2000 historical and actual synthetic aperture radar (SAR) images from ENVISAT ASAR and Sentinel-1A C-SAR, respectively, were used to produce oil pollution density maps of two regions of interest (ROIs) in Indonesian waters. The normalised spill number and the normalised mean polluted area indicate that in general, the marine oil pollution in both ROIs is of different origin: while ship traffic appears to be the main source in the Java Sea, oil production industry causes the highest pollution rates in the Strait of Makassar. In most cases hot spots of marine oil pollution were found in the open sea, and the largest number of oil spills in the Java Sea was found from March to May and from September to December, i.e., during the transition from north-west monsoon to south-east monsoon, and vice versa. This is when the overall wind and current patterns change, apparently making oil pollution detection with SAR sensors easier. In support of our SAR image analyses high-resolution numerical forward and backward tracer experiments were performed. Using the previously gained information we demonstrate that the combination of numerical tracer modelling with (visual) SAR image analyses can be used for an assessment of the marine environment in Indonesian waters, and also helps in better understanding the observed seasonality.