The invention concerns a control device for the movement and positioning of a coupling for a marine loading system (2), said marine loading system comprising at least one fluid transfer line having a line end fixed to a base, and a moveable line end provided with a coupling adapted for connection to a target duct, the system further having a plurality of mechanical connections such that the coupling has at least three degrees of freedom relative to the base, the device comprising at least three proportional control actuators (27, 28, 29) each for proportionally controlling the movement of the system in a degree of freedom, a position sensor (30, 31, 32) of the system tracking each degree of freedom, an operator input interface (60) for inputting commands to move the coupling, and a calculator (41) for calculating the instantaneous position of the coupling from the information provided by the sensors, and for calculating, from movement command inputs of the input interface, simultaneous control instructions to give to each of the actuators such that their combined movements result in a movement of the coupling corresponding to the movement command provided by the operator at the input interface.