The kinematics and dynamics of a floating desedimentation platform, actuated by a planar cable-driven parallel robot with four cables, are presented and illustrated, using an exemplary test setup. As the anchor points are distributed around the reservoir, the resulting large installation space leads to long cables compared to the platform size. It is shown that effects not taken into account in inverse kinematics, such as cable sag and elasticity, have an impact on the solution of the numerically solved forward kinematics. In particular, the positive cable length deviations that occur with small cable forces are critical because they can lead to an ambiguous solution. Regarding the dynamics model, only the translational platform movement is actively controlled, while the platform orientation adjusts passively. It is shown, that there is a neutral platform orientation for each static load condition. Introduced rotational oscillations rapidly decay due to viscous winch friction while a high cable force level reduces the variation of the neutral orientation.