This scientific article is focused on the problem of classifying subaquatic territories. Scientific research was conducted as of 2023. The article introduces a new concept «subaquatic territories», which opens up a new area of research in geoecology, geography, and hydrology. The notions of subaquatic landscapes are examined, as described by various authors in different historical periods. Within the article, fundamental types of classification for these underwater territories are also identified. Special attention is given to the classification methodology of natural rivers developed by D.L. Rosgen and its application for the classification of subaquatic territories. This is significant as such a methodology can serve as an effective tool for studying and systematizing subaquatic resources and landscapes. As part of the research, a classification of subaquatic territories was conducted in a section of the Osetr River basin in the Moscow region. Remote sensing data, particularly the software Google Earth, were used, enabling valuable information to be obtained about the structure and characteristics of the area. The presented results and research methodology hold great potential for practical applications in various fields, such as geoecology, geography, hydrology, as well as engineering and nature conservation studies related to subaquatic territories and landscapes. This opens up new possibilities for further research and improvements in the practical utilization of subaquatic resources and ecosystems. Overall, the article makes a significant contribution to the understanding and systematization of subaquatic territories, offering novel approaches to their classification and revealing the characteristics of the proposed methodology. The obtained results can contribute to a more effective utilization of underwater resources and nature conservation efforts associated with subaquatic ecosystems.