Contents: (1) Introduction. (2) Nature of the deep sea ecosystem. (3) Naturally occurring and fallout radianuclides in the marine environment. (4) Effects of radiation on aquatic organisms. (5) Methods of dosimetry for aquatic organisms and an estimate of the background dose rate in the deep sea. (6) Derivation of dose rates to organisms based on the IAEA definition of high level radioactive waste unsuitable for dumping at sea. (7) Dose rates arising from actual sea dumping at sea. (8) Summary and Conclusions.