AIM: A high resolution, digital marine airgun seismic reflection survey and a shallow resolution, analogue marine boomer seismic reflection survey, plus secondary echosounder bathymetry and side-scan sonar topographic surveys, were carried out for BHP Petroleum Pty Ltd in two phases, during June and December 1992, over separate 3.0x3.75 km and 2.5 km square grids of survey lines centred on the proposed Borda 1 offshore drilling locations (original and revised). The purpose of these site surveys was to check the sea floor for suitable drilling rig anchoring conditions, and to identify potential local drilling hazards, e.g. near-seabed shallow gas accumulations, which might occur in the uppermost continental shelf section. Analogue boomer seismic records would be used to determine shallow sub-seabed geology within the top few tens of metres of sediment, based on their acoustic characteristics, while stacked digital airgun seismic displays would be used to interpret the intermediate casing zone geology to depths of approximately 1000 metres subsea. METHODS: Survey dates: 14-21/6/92 (Borda); 3-10/12/92 (Borda Extension). Energy source: Airgun. CDP coverage: 4800% (digital survey only). Recording mode: 48 channel (digital survey only) - TTS 128 recorder. SP interval: 6.25 metres, group interval: 6.25 metres. 38 line km (Borda) and 9 line km (Borda Extension) of digital data along 47 and 32 lines respectively were acquired by contractor Racal Survey Australia Ltd, using the M/V 'Tilbata Creek' for phase 1 and the M/V 'Pacific Oak' for phase 2, working out of Port Lincoln. Processing was done by Racal in Kuala Lumpur, Malaysia, and the interpretation was also done in-house. RESULTS: No significant anchoring or drilling constraint is noted at the proposed Borda 1 location. Drilling is expected to encounter 2 high amplitude seismic anomalies at depths of approximately 577 metres and 1034 metres subsea respectively. Although no acoustic masking indicative of gas is apparent, caution is advised when drilling approaches these levels. The anomalies are believed to be associated with coarser sediments and/or differential compaction.