The use of simple GIS and GPS techniques as tools supporting field data collection in the process of macrophyte-based assessment and classification of the ecological status of lakes is described in the paper. The ecological status of Lake Długie was determined with traditional water quality evaluation methods, including the “anchor” or “diving and GIS” method. Obtained results show simple GIS techniques for registering submerged plant communities supplemented with terrain investigations involving scuba diving, producing more accurate data than those acquired with traditional methods.