The major impact of artificial radioactive material on the oceans has been as a potential pollutant, and, in particular, concern has centred on the public health problems that might arise through human exploitation of marine environments. This public health problem has been an important stimulus to marine pollution methodology. The development and deployment of critical path analysis techniques to the control of this material and to the assessment of its significance for human radiation exposure (Preston 1969; Foster, Ophel and Preston 1971; Slansky 1971) not only exemplifies the control of a chemical pollutant but has served as a stimulus to produce much of the basic physical, chemical and biological data required for its proper implementation. In more recent years the advantages which labelled environments confer for studies of a much wider physical, chemical or biological nature are being increasingly recognised (Natn. Sci. Fdn 1971; Volchok et al. 1971; Lowman, Rice and Richards 1971; Duursma, 1972; Preston, Jefferies and Pentreath 1972,) and many of the tools of nuclear technology, radio-isotopes, reactor propulsion systems, isotope power sources, neutron activation analysis techniques, etc., will enjoy an increasingly important role in oceanography, not only in basic investigations but also in the rational exploitation of marine resources.