Cartography of littoral rocky-shore communities (CARLIT) is a European Union Water Framework Directive - compliant monitoring method which assesses ecological quality of coastal sea waters. It is based on visual observation and mapping of geomorphological features of the coast and dominant species of macroalgae that serve as bioindicators (Biological quality elements). The research began in May 2020 and was conducted along the coastal waters of the town of Opatija, which was then divided into five monitoring stations. In addition, with the assessment of the ecological quality of seawater, the objectives of this study were a methodological review of the CARLIT method and a comparison with the results of similar studies in Istria and Kvarner Bay. The research showed poor ecological quality of seawater at the stations Volosko, Opatija-Istok, Opatija-Centar and Ičići, while the station Opatija-Zapad was of moderate quality. The obtained results of EQR values in this study differed significantly from the ones previously carried out in the same area in 2017. due to differences in the length of the researched coastline. The CARLIT method has proven to be a reliable tool for assessing the ecological status of marine waters due to its simplicity and precision in determining the dominant communities and localized anthropogenic impacts on the area.