Abstract: Introducing the design scheme and analysing the experimental results, the paper proves that the X-band liquid level guage made according to the FM-CW principle can be used on semi-submerged drilling well platforms. The theory and practice indicate that the operating distance to sea level is more than 30 meters for all weathers. Three static parameters:the water depth, the transversal and longitudinal dip angles are measured above waving sea using appropriate automatic data processing and the accurancy of the measurement is satisfying.