## 6 Conclusions  
This study is based on an authentic salvage case involving coordinated efforts of two lifting barges to salvage a shipweck. The process of shipw salvage, from disengaging from the seabed to partially surfacing, is divided into three stages. A unified criterion is established by incorporating the three parameters of MA, RMS, and CV to enable a quantitative evaluation of safety under various working conditions. The manuscript explores the ship's motion responses and the tension responses of lifting cables. The conclusions drawn in this manuscript are as follows:  
1. Effects of waves in different directions:  
(1) In most scenarios, curves representing the maximum tension values of cables numbered 1-15 and 16-30 exhibit a \"middle part drooping\" shape distribution. The closer cables are to the ship's midsection (cables 7-9, cables 22-24), the slower the curve sags. The tension of the lifting cables responds most strongly to waves in the 180\({}^{\circ}\) direction, while the tension response is minimal under waves in the 90\({}^{\circ}\) direction, indicating better safety performance. (2) A comprehensive analysis of motion response and tension response reveals that the heave response determines the total tension value of the lifting cables. Additionally, the roll and pitch responses determine the discrete degree of tension distribution in the lifting cables. (3) Based on quantitative assessment criteria, recommended operational windows for salvage operations to enhance the three ships' safety include adjacent wave areas in the 0\({}^{\circ}\) and 180\({}^{\circ}\) directions. Additionally, wave intervals in the (115\({}^{\circ}\), 155\({}^{\circ}\)) and (205\({}^{\circ}\), 245\({}^{\circ}\)) directions can be selected. For improving the safety performance of lifting cables, wave directions of 90\({}^{\circ}\) and 270\({}^{\circ}\) are preferable, while salvage operations under waves in the 0\({}^{\circ}\) and 180\({}^{\circ}\) directions should be avoided. Taking all these factors into account, wave intervals in the (115\({}^{\circ}\), 155\({}^{\circ}\)) and (205\({}^{\circ}\), 245\({}^{\circ}\)) directions are considered as the most suitable operational window for salvage operations. 2. Effects of connection cables among the three ships:  
(1) To constrain the motion responses of the three ships, arranging inclined lifting cables underwater is the optimal solution. Arranging connecting cables that are 1-1.2 times longer than the salvage spacing between the two lifting barges on the water's surface is reasonable. However, the tension in the connecting cables that are 1-1.1 times longer than the salvage spacing fluctuates significantly. Thus, connecting cables that are 1.1-1.2 times longer than the salvage spacing is more suitable. (2) In terms of enhancing the safety performance of lifting cables, inclined lifting cables also yield positive results. 3. Effects of lifting cable breakage:  
(1) Whether lifting cables break under the action of waves in the direction of 135\({}^{\circ}\) or 180\({}^{\circ}\), the safety factor curves of the rest of the lifting cables (1-15 as a group, 16-30 as a group) generally present a \"middle part drooping\" shape distribution. The shape of the tension increase in the remaining lifting cables differs, presenting a \"middle part drooping\" or a \"middle part uplifting\" shape distribution. It is more dangerous for lifting cables to break under the action of waves in the direction of 180\({}^{\circ}\). (2) After lifting cables break, the cables next to them have the most significant fluctuation. The lifting cables at the bow and stern ends should be strengthened to prevent breakage. Salvaging a shipwck constitutes a unique operational mode.