The primary objective of Working Group 2 of Project MARINA was to consider recent measurements of environmental radioactivity in north European waters and to use this, and other information, to report the likely magnitude of doses to the critical group from marine pathways. The monitoring data were supplemented, where appropriate, with predictions from simple models. The major sources of radioactivity studied were as follows: (i) liquid wastes from nuclear fuel reprocessing plants; (ii) liquid wastes from nuclear power plants and other major nuclear industry sites; (iii) solid waste disposal in the deep north-east Atlantic; (iv) fallout from Chernobyl; and (v) naturally-occurring radionuclides. Some of the largest doses from marine pathways are predicted for naturally-occurring radionuclides. In this case, the dominant radionuclide is polonium-210 and the dominant pathway is via consumption of molluscan species. The highest doses from the nuclear industry were due to the operation of the reprocessing plant at Sellafield. Discharges from this site have been decreasing substantially in recent years and, as a consequence, doses have also been reducing. (author).