A device for controlling trimming flaps (12, 13) of a watercraft (10), preferably having two trimming flaps (12, 13) and in each case at least one hydraulically operated for adjustment of the inclination angle (15) of the associated trimming flap (12, 13). The invention provides that the or each hydraulic system (18) has an associated flowmeter (21) which detects the flow of hydraulic fluid in the hydraulic system (18) in order to determine the inclination angle (15) of the associated trimming flap (12, 13). This makes it possible to dispense with external measurement devices for detection of the position of the trimming flaps, for example appropriate position sensors. The invention also relates to a corresponding method, and to watercraft having a corresponding device.