Abstract: As a widely used mariculture facility in China’s sea areas, the hydrodynamic performance of gravity net cages is crucial for ensuring the aquaculture safety and efficiency improvement. However, few studies have been conducted on the hydrodynamic performance of square-type submersible net cages. Thus, we used Orcaflex software to establish a model for the hydrodynamic response of a square-type submersible net cage, so as to investigate the hydrodynamic response under combined wave and current conditions. It is found that the change of incident wave angle had a significant effect on the force distribution of the cable of net cage, and the force on the cable was significantly greater on the weather side than on the lee side. When the wave angle ranged from 0° to 45°, the maximum effective tension of the cable was almost unchanged, which indicates that the arrangement adopted in the study is able to well resist the waves with various angles. In addition, we analysed the hydrodynamic performance of the square-type submersible net cage under extreme sea conditions was analyzed. The results show that the effective tension of the cable, the degree of deformation of the net, and the maximum acceleration and amplitude of motion of the pontoon, all decreased significantly when the net cage was submerged. This findings effectively prove that the submerged state of net cage is more helpful in resisting extreme sea state, and improving the fishing suitability of equipment.