Hulls of 9 boats operating in inland waterways and coastal Baltic waters along were examined for the presence of fouling organisms. A total of 23 animal taxa were recorded, 8 of them being alien species known to have been earlier introduced into the Baltic Sea basin. The most frequent taxa were: Amphibalanus improvisus, Chironomidae, Dreissena polymorpha, and Gammarus tigrinus. The fi ndings of this study clearly demonstrate the important role potentially played by small crafts in the introduction and spread of alien species not only in the River Odra estuary, but also in the coastal Baltic waters outside of the Odra plume.