Reports describe an offshore sampling survey conducted of the topmost seabed sediments in a portion of Gulf St Vincent, over six days (non-consecutive) during December 1974 and January 1975. The aim was to map the occurrence and estimate the volume of loose shelly sediment and lime sand material, as a way of gauging the development potential of this resource for a low cost raw material to use in cement manufacture. The survey area was located ~5 miles offshore from Port Adelaide and extended north-south for ~ 11 nautical miles, i.e. covering roughly 420 square miles where the water depth ranges from 38 feet to 96 feet. As an adjunct to the main survey, an environmental marine flora and fauna base line data collection survey of the area of interest for possible underwater mining was also separately undertaken between April and October 1975.