Abstract: The paper presents the visualisation and monitoring of marine pollutant aggregations as the sample application of the real-time, remotely accessible marine GIS. The system is dedicated for instantaneous integration, processing and visualisation of marine data acquired by direct sampling, satellite remote sensing and underwater acoustic systems. The developed Web-based GIS is capable of producing 2D maps with overlaid various types of data, as well as generating the composed, time-varying 3D scenes presenting different elements of marine environment. As the sample application of the system, the visualisation of the 3D modelling of an oil spill drift and spreading within the southern Baltic area is presented. The data were obtained from the composed 3D modelling system CAROCS. The developed GIS, due to its remote accessibility and the on-line data processing, may be applied as a useful tool for maritime domain awareness and emergency management supporting, with respect to hazard of a different kind: pollution, ecological catastrophes, natural disasters. The system utilises the SQL spatial database for data storage and the Scalable Vector Graphics (SVG) and Virtual Reality Modelling Language (VRML) standards for remote presentation of geographical objects, and requires only the WWW browser with SVG and VRML viewer on the client side.