The Roof-attached Vortex (RAV), Floor-attached Vortex (FAV) and Combined Submerged Vortices (CSV) induced by the closed sump of a tidal pumping station have become an intricate problem that urgently needs to be clarified in expanding the stable operation range of units. This work reveals the dynamic evolution laws of various vortices and their typical forms under different flow conditions based on a combination of high-speed visualization and scale-resolving simulation methods. The results show that the RAV is a single spiral vortex structure under low flow rates and a main-secondary vortex double spiral structure under high flow rate conditions. The increase in flow rate has a positive promoting effect on the growth of the FAV. The RAV and FAV frequency values of occurrence are in the range of 0.001–0.1 Hz and 0.007–0.06 Hz, respectively. The maximum frequency of the CSV is 0.03 Hz. In the symbiotic stage of the CSV, there is an interaction between RAV and FAV. The suction of the surrounding low-pressure system affects the FAV, with vertical vorticity propagating towards the side of the RAV. In addition, the tangential velocity distribution of RAV and FAV exhibit rigid-like rotation characteristics consistent with the Burgers vortex model. •Typical morphology and evolution characteristics of various vortices in a closed sump have been revealed.•The frequency of multiple vortices occurring is statistically analyzed.•The instantaneous characteristics of dynamic parameters of the combined submerged vortices are explored.•The roof-attached and floor-attached vortex exhibit tangential velocity distribution characteristics like rigid-body rotation.