AbstractFrom 2002 to 2005 a FerryBox system was installed aboard two different ferries travelling between Cuxhaven (GE) and Harwich (UK) on a daily basis. The FerryBox system is an automated flow-through monitoring system for measuring oceanographic and biogeochemical parameters installed on ships of opportunity. The variables were recorded in a time interval of 10–20 seconds corresponding to a spatial resolution of about 100 m. The dataset provides the parameters water temperature, salinity, dissolved oxygen and chlorophyll-a fluorescence. There is a longer data gap between November 2002 and August 2003 in the time series due to a change of the vessel in October 2002. The data are available at doi:10.1594/PANGAEA.883824 and as part of the COSYNA data portal CODM at http://codm.hzg.de/codm or doi:10.17616/R3K02T.