Inland waterway transportation and hydropower development projects play an important role in promoting social progress.However,the widespread development of underwater karst caves has seriously affected the site selection and construction of such projects.This paper proposes an underwater resistivity tomography imaging detection scheme,which is applied to Xiajijiao Navigation and Hydroelectric Hub Project in Dongjiang,Guangdong Province.A total of six 700-meter-long cross-river survey lines are laid out,with each underwater cable arrangement containing 40 electrodes spaced 5 meters apart,and adjacent arrangements repeat observations every 100 meters.The inverted three-dimensional electrical structure delineates key geological units such as high-resistance gravel layers,low-resistance sandstone and high-resistance limestone,and multiple concealed karst cave target areas are identified in combination with existing borehole data.Underwater resistivity tomography imaging poses great construction difficulties and involves complex forward and inverse calculations,the research results can provide references for subsequent resistivity tomography imaging and underwater geological anomaly detection.