The 21-meter long, 170 ton fishing vessel Mare Liberum became disabled off the Dithmarscher Coast.  The Mare Liberum had a hydraulic pump failure which left the rudder blocked.   The 2 men on board contacted the German Maritime Rescue Service (GMRS)  located at Busum.   The GMRS launched the rescue boat SK-33 which took the Mare Liberum under tow back to Busum.