The prevailing paradigm in organic- rich shale development posits a strong association with deep anoxic environments. This view suggests that the deeper parts of deep- to- semi- deep lakes, located in the basin' s sedimentary subsidence centers, provide the anoxic reducing conditions conducive to the formation of high- quality source rocks. However, observations of organic matter enrichment in modern water bodies challenge this established notion, underscoring the need for a comprehensive examination of the relationship between water depth and organic matter accumulation. To address this, the present study integrates data on dissolved oxygen distribution in water bodies and organic matter content in surface sediments of modern lakes, drawing from environmental and ecological sciences, to investigate the enrichment characteristics of organic matter at different depths in enclosed water bodies. The results demonstrate that dissolved oxygen concentrations in water bodies increase with depth, indicating that the bottom layers of lakes and seas are, in most cases, oxygen- rich environments. Deeper water bodies exhibit lower primary productivity and are not necessarily characterized by low- energy or anoxic conditions, which are less conducive to the preservation of organic matter. In contrast, relatively enclosed environments, such as lagoons, bays, and lake bays, serve as more effective depositional settings for the accumulation of organic matter, minerals, volcanic ash, and other materials. This study concludes that in smaller enclosed to semi- enclosed water bodies, shallower depths are more favorable for the enrichment of organic matter. Furthermore, the contribution of exogenous organic matter cannot be ignored, as it plays a significant role in the overall enrichment process. Conversely, open water bodies, such as deep continental shelves and larger deep- to- semi- deep lakes, lack the necessary conditions for the development of high- quality source rocks.