A docking device for the mechanical connection, namely for the docking and undocking of an upper container module of a multi-part container for a fluid, and a lower container module of the multi-part container, wherein the docking device comprises an upper docking segment, which can be attached to an opening of the upper container module with an upper connecting means, and a lower docking segment, which can be attached to an opening of the lower container module with a lower connecting means, wherein the docking device is designed such that the fluid then passes from the upper container module through a duct of the docking device into the lower container module, as conditioned by gravity and/or pressure, or from the lower container module into the upper container module as conditioned by buoyancy and/or pressure, if at least one valve body, which can be moved by means of an actuating arrangement arranged in the upper, and/or in the lower, docking segment (3, 5), is located in the duct of the device in an open valve body position, an upper duct section is arranged in the upper docking segment, and a lower duct section is arranged in the lower docking segment, an upper docking region of the upper duct section and/or of the upper docking segment, and a lower docking region of the lower duct section and/or of the lower docking segment, can be arranged in a fluid-tight manner in one another, and/or on one another, in particular by means of a form-fit, and/or a force-fit, connection, such that the fluid flows through the outwardly-sealed duct when the valve body is in the open position, and an actuating arrangement is arranged in the upper duct section and/or in the lower duct section, by means of which the valve body can be actuated such that it can be moved from an open valve body position into a closed valve body position, or from a closed valve body position into an open valve body position, characterised in that, the actuating arrangement comprises at least one locking arrangement, comprising at least one locking means, wherein upper and lower docking segments (3, 5) can be stably connected to one another, in particular can be locked, by the movement of the locking means into a locking position, wherein during the docking process, when the actuating arrangement is actuated, the locking means can first be actuated, and then the valve body, and during the undocking process, when the actuating arrangement is actuated, the valve body can first be actuated, and then the locking means. the docking device comprises an upper docking segment, which can be attached to an opening of the upper container module with an upper connecting means, and a lower docking segment, which can be attached to an opening of the lower container module with a lower connecting means, wherein the docking device is designed such that the fluid then passes from the upper container module through a duct of the docking device into the lower container module, as conditioned by gravity and/or pressure, or from the lower container module into the upper container module as conditioned by buoyancy and/or pressure, if at least one valve body, which can be moved by means of an actuating arrangement arranged in the upper, and/or in the lower, docking segment (3, 5), is located in the duct of the device in an open valve body position, an upper duct section is arranged in the upper docking segment, and a lower duct section is arranged in the lower docking segment, an upper docking region of the upper duct section and/or of the upper docking segment, and a lower docking region of the lower duct section and/or of the lower docking segment, can be arranged in a fluid-tight manner in one another, and/or on one another, in particular by means of a form-fit, and/or a force-fit, connection, such that the fluid flows through the outwardly-sealed duct when the valve body is in the open position, and an actuating arrangement is arranged in the upper duct section and/or in the lower duct section, by means of which the valve body can be actuated such that it can be moved from an open valve body position into a closed valve body position, or from a closed valve body position into an open valve body position, characterised in that, the actuating arrangement comprises at least one locking arrangement, comprising at least one locking means, wherein upper and lower docking segments (3, 5) can be stably connected to one another, in particular can be locked, by the movement of the locking means into a locking position, wherein during the docking process, when the actuating arrangement is actuated, the locking means can first be actuated, and then the valve body, and during the undocking process, when the actuating arrangement is actuated, the valve body can first be actuated, and then the locking means.