## 4 Conclusions  
This study focuses on a new type of single-point mooring gravity-type deep-water (SPM-GDW) cage. A numerical model of the SPM-GDW cage is established using the OrcaFlex software. The response characteristics of different components of the cage under irregular wave and current conditions are analyzed from three aspects, i.e., the cage motion, the mooring line forces, and the floating collar stress. Analyses on response time history curves, wave elevation time histories, and spectral density statistics were conducted. The main conclusions are given as follows:  
1. In terms of cage motion response, the heave motion of the cage is mainly impacted by the wave conditions rather than the currents, while the surge motion of the cage is closely related to currents. As the current velocity increases, the surge motion of the cage changes significantly. The heave motion of the cage is consistent with the wave elevation in the vertical direction. As the current velocity increases, the response of the heave motion exhibits a slight delay when compared with the wave elevation, but the effect is minimal. The lag effect of the cage's surge motion relative to the wave elevation is significant and becomes more pronounced as the current velocity increases. The heave and surge motions of the cage are primarily influenced by wave load frequency. The high-frequency loads have less effect on the heave and surge motions of the cage. Under wave and current conditions, low-frequency loads have a significant impact on the surge motion of the cage. 2. The current velocity has a significant effect on the mooring forces and floating collar stresses. The simulation results show that under the wave and current loads, as the current velocity increases, the mooring forces and floating collar stress of the cage increase significantly. There is a correlation between wave elevation and mooring line tension, with peak tensions occurring almost simultaneously with peak wave elevations. In addition, the correlation between wave elevation and peak stress on the floating collar is also observed, with peak stresses occurring at the peak of the wave elevation. However, the floating collar stress exhibits high-frequency response characteristics while satisfying the trend of wave frequency response. Spectral density analysis reveals that the maximum peak values of the spectral density of mooring forces and floating collar stress in the SPM-GDW cage system correspond to the peak of the wave spectrum. The current velocity has a significant impact on the spectral density of mooring tension and floating collar stress in the low-frequency range. As the current velocity increases, the spectral density values of mooring tension and floating collar stress also increase. Under high-frequency loads, the spectral densities of mooring line tension and floating collar stress are negligible at high frequencies. Figure 19: Spectral density of floating collar stress under irregular waves and current. 3. It was proved that the design of the mooring line, anchor, and floating collar of the novel SPM-GDW net cage presented in the research can meet the safety requirements. But there are some points that need to be paid attention to in the following research. For example, the high-frequency response of the floating collar that may lead to fatigue failure, the applicability of different wave spectra, the novel anchor design for ensuring the safety of the new SPM net cage, the comparative analyses on cost-effectiveness between the novel SPM-GDW net cage and traditional MPM-GDW net cage, and so on. All in all, this study provided a new type of SPM-GDW net cage for mariculture, and the structural response characteristics identified in this study provide a computational basis for the optimized design and analysis of such cages. Conceptualization, G.P. ; methodology, C.W. and L.S. ; software, C.W. and L.S. ; validation, G.P. and S.Z. ; formal analysis, S.Z. and H.L. ; investigation, G.P. ; resources, X.H. ; data curation, T.Y. and Y.H.