The innovative investigation on the mechanisms for remobilisation and bioavailability of removed radionuclides from nuclear facilities allows researchers to gain a better insight on marine environmental radioactivity. The REMOTRANS project evaluated the radiological consequences and transboundary exposure including uptake in biota and radiological modeling. Key objectives were to optimise European expertise in the field of environmental radioactivity and encourage transfer of skills as well as training of young researchers. The project work resulted in an improved inventory of radionuclide estimates for five major marine waters involving contaminated sediments. This inventory provides an overview of the contamination and allows comparisons with earlier studies. The project also allowed for the exploration of the differences in the extent of translocation between remobilised radionuclides and direct discharges. In addition, comparisons of the bioavailability of radionuclides released from contaminated sediments to those coming from recently released activity were also performed. Emphasis was put on the role that environmental parameters, radionuclide speciation and solid partitioning in sorption/desorption processes at the sediment-water interface play. Thereby, a comprehensive study on the processes controlling radionuclide remobilisation from contaminated oxic and anoxic sediments was also conducted. Moreover, research work involved modelling of the remobilisation, the transport and the sedimentation including transport and sedimentation of new releases as well as observed concentrations in water samples and indicator species. The REMOTRANS project results could contribute to a more informed debate on waste management of controlled releases of radioactivity in the marine environment. They provide the basis for information to the public, the news media and politicians about current developments and might be useful in emergency situations.