The data set contains a variety of physical, chemical and biological parameters. Hydrographic profiles provided temperature, salinity, fluorescence, dissolved oxygen and transmissance measurements, which were supplemented by time series of surface ocean and meteorological properties. Time series of current velocities, temperature and sea level were also collected. Biogeochemical and biological analyses of water samples provided nutrient, phytoplankton and zooplankton data, while production data were derived from incubation experiments. The data were collected at seven stations in the Celtic Sea with varying physical and biological characteristics. Fieldwork was undertaken between 15th and 29th May 2000, with each station being occupied for 24 hours. Data were collected via shipboard deployment of CTD profilers and undulators with accompanying auxiliary sensors, and discrete water sampling. Further data were obtained from three moorings including acoustic Doppler current profilers (ADCPs), temperature recorders and bottom pressure recorders that were also deployed and recovered during the study period. Measurements were collected during RRS Discovery cruise D246 as part of the multidisciplinary study of the interactions between physical processes and biological production in contrasting pelagic shelf waters. An additional goal of the study was to map the tidal front situated in the St George's Channel. The study was co-ordinated by Plymouth Marine Laboratory and the research involved 28 scientists and technicians from 14 separate institutions situated in five different countries. Data are managed by the British Oceanographic Data Centre.