Hence, this study establishes a theoretical model of the cable of the CLB system, wherein the grounding length is a variable. The model proposed in this study treats the static mechanics of the cable, which is essential for determining a base configuration used for a dynamic analysis of the cable. This paper presents the governing equations of the model and a method for solving the equations. Using the theory proposed in this study, we discuss the changes in the grounding length in response to the distance between two ships and the length of the submerged part of the cable.