Scientific Diving techniques were employed during a 54 day oceanographic research cruise to the Bellingshausen Sea, Southern Ocean (65°S–72°S, 80°W–87°W), in order to position sampling and data collecting instrumentation beneath sea ice. Eight Scientific Divers and a Field Diving Officer safely completed 112 individual dives (range 2–80 minutes, 2–28 m); 94 of these were roped dives through holes cut in 1 m thick sea ice. Seawater temperature was −1.8°C, horizontal visibility 30 m+ and water depth 600 m or more. No problems were encountered with the diving equipment used. Diving techniques enabled the collection of an important data set describing the dynamics of phytoplankton and zooplankton growth beneath sea ice. Recommendations for future under-ice oceanic scientific diving inc1ude the use of dive tables with ascent rates of less than 15 m/min, the provision for therapeutic oxygen at the dive site, and adequate shelter for surface tenders.