A cable-driven parallel robot (CDPR) is a mechanism that controls the position and attitude of an object using multiple cables. We propose an underwater cable-driven parallel robot (UCDPR), which is a CDPR composed of multiple surface robots. A UCDPR is a type of mobile cable-driven parallel robot (MCDPR) that is composed of multiple mobile robots and is an underwater application of MCDPR, which has been used only on land and in the air. We describe the details of the operational scenario of the UCDPR, from landing on the water to executing a task. We also simulated numerically the stabilization phase required after landing on water and the trajectory tracking control phase required for underwater exploration and other tasks. In this numerical simulation, we used a high-gain feedback controller as the trajectory tracking controller to add robustness to the control system. As a result, a trajectory tracking control was realized within a tolerance tracking error range of 10−2 m underwater in the presence of a maximum current velocity of 0.8 m/s (≅ 1.5 knots), which is a control requirement.