Underwater NaI(T1) and HPGe detectors are used in the environmental measurements programs at the Savannah River Site (SRS). A 22.9 cm × 10.2 cm NaI(T1) detector on the Savannah River continuously monitors effluent releases from both SRS (DOE) and Plant Vogtle (Georgia Power). Correlations with known releases indicate a sensitivity of 4 mBq/l for58Co with 1500 min spectra; such levels are well below those of hazardous or legal concern. A 30%-efficient HPGe detector has appraised radionuclides in SRS cooling pond sediments; the dominant gamma-emitting radionuclide detected was137Cs, at levels ranging up to 2.0 MBq/m2. The pond activities were adequately quantified by 1 min counts with the HPGe detector; resulting contour maps of sediment137Cs provided guidance for partially draining the ponds for dam repairs.