A clean environment is often taken for granted, but when a river or a lake becomes polluted, it might be hard for the general public to verify the condition. A simple visualization tool for checking the condition of water could help to inform the public and help to increase environmental awareness. With the emergence of Open Data and other openly available data sources, it is possible to create new and innovative applications. In this paper we present a web-based tool for reviewing the quality of water by applying the River Heavy Metal Evaluation Index (rHMEI) method together with open data on water quality in Finland.