Hydrodynamic load constitutes a critical parameter in the design of offshore aquaculture cages. However, the current severe deficiency in research on the hydrodynamic characteristics of flow-diversion and drag-reduction cage systems significantly constrains their safety design and structural optimization. This study systematically analyzes the influence of common offshore aquaculture cage geometry, net solidity, and inflow velocity on hydrodynamic loads based on physical model experiments. The experiment measured the hydrodynamic loads on square, hexagonal, octagonal, dodecagonal, and circular cages under steady flow conditions (flow velocity range: 0.3 m/s to 0.7 m/s at 0.1 m/s intervals). The results demonstrate that hexagonal cages exhibit significant flow-diversion and drag-reduction performance under both constant and varying conditions of net solidity and flow velocity. Under identical net configuration conditions, the mean hydrodynamic loads and their sensitivity to flow velocity across various cage types exhibited the following increasing order: hexagonal < octagonal < circular < square < dodecagonal. Among them, the hexagonal cage demonstrated approximately 78% of both the hydrodynamic load and flow-velocity sensitivity compared to the square cage. This study provides critical reference data for structural optimization of aquaculture net cages.