Site selection for Site 1163 was based on a SCS survey conducted during the R/V Melville cruise Boomerang 5 in 1996. A 1.6-hr SCS and 3.5-kHz PDR survey was conducted on the approach to Site 1163 (JOIDES Resolution [JR] SCS line S11; Fig. F18) to ensure the correct site location by comparing the GPS-navigated SCS data with the previous SCS image and to verify sediment thickness. The water gun was triggered at a shot interval of 12 s, equivalent to ~31 m at 5.1 kt (the ship's average speed). A 1.5-km-wide basin structure is revealed in this profile between shotpoints 270 and 310 (Fig. F19). Site 1163 is close to the prospectus site AAD-3b (AAD = Australian Antarctic Discordance) at a position corresponding to shotpoint 292 of the seismic profile. Sediment cover was estimated to be from 5.88 to 6.01 s in two-way traveltime, equivalent to at least 130 m (see Fig. F19). We washed through 161 m of sediment in Hole 1163A before basement was reached.