A device (1) for providing information on positioning of at least one moveable coupling (26) of a marine loading system (2), the system comprising at least one fluid transfer line having a line end fixed to a base (21), and a moveable line end provided with a coupling (26) adapted for connection to a target duct, the coupling or a member immediately neighboring the coupling having at least one means for providing information on the positioning of the coupling (33) either adapted to cooperate directly with a means (34) for providing information on positioning of the base disposed on the base or on a member immediately neighboring the base to provide, on the basis of the information on positioning of the base, information on relative positioning of the coupling directly relative to the base, or adapted to provide information on absolute positioning of the coupling (26) in space, and, the base having a fixed position in space, the device has a calculating means making it possible to calculate on the basis of the information on absolute positioning of the coupling and data on positioning of the base fixed in space, information on relative positioning of the coupling directly relative to the base.