The implementation of the sustainable development objectives, requires additional knowledge about underwater landscapes of inland reservoirs. In this article, we assumed that (1) underwater landscapes of lakes are shaped mainly by the type of substrate and the assemblages of flora and fauna inhabiting a given reservoir; (2) vegetation is one of the most important elements of underwater landscapes, which dynamically reacts to environmental changes. This article presents the results of a study on the underwater landscapes of Lake Wielki Staw in the Karkonosze Mountains. Thirteen types of underwater landscapes were distinguished in the lake based on underwater inventory and spatial analysis using ArcGIS 10.7 software. The level of changes that occurred in the underwater landscape studied was determined using the underwater landscape structure maps for 2005, 2011, 2017, and 2021. In addition, the landscape change index ( LCI) for Lake Wielki Staw was determined for 2005–2011, 2011–2017, and 2017–2021. The results obtained indicate that underwater landscapes in lakes, similarly to terrestrial landscapes, are dynamic and subject to changes. In the case of Lake Wielki Staw, the changes in the range of Isoëtes lacustris communities in individual parts of the lake limited the differences in the area of all types of underwater landscapes distinguished. This allows us to use underwater vegetation inhabiting a given reservoir as an indicator of changes in underwater landscapes. Keywords: