This dataset contains data collected during the integration and demonstration of the newly developed SenseOCEAN multifunctional sensor package. The data were collected from field tests in Kiel Fjord (Germany), the Baltic Sea and the Mediterranean Sea in September 2016 and May 2017. New marine chemical sensors (such as optode sensors (O2, CO2, NH3, pH), lab on chip (LOC) sensors (NO3-, NO2-, PO43-, Fe2+, pH) and electrochemical sensors (silicate, N2O)), an integrated multifunctional sensor, plug and play Modbus module and data assembly centre were developed by the EU consortia, SenseOCEAN. The consortia consisted of TU Graz, Pyro Science GmbH, Chelsea Technology Group, Aarhus University, Alfred Wegener Institute (AWI), CNRS-LEGOS, Max Planck Institute, nke Instrumentation, TE Laboratories, University of Southampton, National Oceanography Centre (NOC), Unisense A/S and the British Oceanographic Data Centre (BODC). The sensors and Modbus module were deployed for demonstrations on various platforms including CTD Rosettes, fixed-position pontoons and NKE PROVOR profiling (ARGO) floats. The data were collected as part of the SenseOCEAN Collaborative Project funded by the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement No. 614141. The main aim of the SenseOCEAN project was to develop new chemical sensors for in situ measurements of the marine environment and to combine these to produce an integrated multifunctional biogeochemical sensor package. The coordinator was Professor Douglas Connelly at the National Oceanography Centre, Southampton, UK. The data are held by BODC as a series of ASCII data files conforming to the NASA AMES 1001 format together with a PDF document that describes the data set.