The distribution of surface water is highly dynamic both spatially and temporally, and very sensitive to climate change and anthropogenic interference, especially in highly urbanized regions. The abundance of surface water and its spatiotemporal distribution indicate the availability of water resources and the difficulty of water development and utilization. Consequently, it is essential to perform reconstruction and trend prediction of surface water body changes with high accuracy in time and space for scientific research as well as for practical purposes such as flood prevention, sustainable development of water resource systems, and regional ecological management. The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is highly developed economically and societally and is characterized by a subtropical humid monsoon climate with an extensive distribution of surface water bodies. Under the integrated pressure of continuous natural environmental change and intense human activity, concerns regarding both the water environment and water security in this area is increasing at an unprecedented rate. In this study, we collected water distribution information from 2001 to 2020 at 5-year intervals, as well as annual and monthly water extent dynamics data for the GBA from the Global Land Analysis & Discovery database. Subsequently, the spatial and temporal changes in water extent, frequency, and distribution characteristics in the last two decades were investigated using remote sensing and geographic information system methods. Finally, elastic analysis was conducted to identify the sensitivity of water body changes to changing environmental parameters, including precipitation, temperature, and urbanization. Focusing on the national and regional strategic needs of GBA, the research objectives of this study were to explore the mechanism of temporal and spatial dynamics of the water extent and frequency, trace the volatile areas of regional water changes, clarify the driving factors of water distribution changes, and provide a basis and guidance for comprehensive management of water resources, flood disaster prevention, and control in areas with high human activity. The first result shows that in the last two decades, the water extent and frequency of the GBA are on a decreasing trend, with an average decreasing rate of 50, 31, and 11 km2/a for maximum, annual, and permanent water extent, respectively, while a large proportion of seasonal water bodies changed into permanent and flood-prone bodies during the same period. Second, although the water frequency showed distinct spatial and urban/rural heterogeneity, it was on a decreasing trend in most of the GBA, except in the eastern region. A steeper decline was observed in urban areas, especially the emerging urban regions. Third, the dike-pond system decreased both in water extent and frequency, while the large and medium-sized lakes and reservoirs in the upper catchment increased in extent. Finally, elastic analysis suggests the dominant driving factor of regional water body change is land use change, which contributed more than 80% to the decrease in water extent, and the reservoir increase is mainly due to precipitation change. The results of this research provide scientific guidance for regional water resource guarantee, water environment optimization, and sustainable development promotion. In addition, this research can serve as a decision-making reference for the development of the "One Belt One Road" national strategy and Guangdong-Hong Kong-Macao Greater Bay Area. [ABSTRACT FROM AUTHOR]