This record describes multibeam echo sounder data collected during field experiments on RV South Cape survey SC2020_V01. CSIRO’s Oceans & Atmosphere Shallow Survey Facility (SSF) undertook multibeam water column experiments over an artificial seep deployed near Kingston Beach, southern Tasmania. The goal of the experiments was to characterize the utility of high frequency multibeam water column data for the detection of gas seeps in very shallow water (<20 m). These experiments were aligned to inform the ANLEC R&D Carbon Capture and Storage Marine Monitoring and Verification (MM&V) project (ANLEC R&D 7-0816-0305) on the application of multibeam water column data for the detection of gas seeps in shallow water as a regular monitoring tool. The Geophysical Survey & Mapping team single-head EM2040C multibeam was mobilised on RV South Cape and bathymetry and water column data were collected over a custom-built bubble release system to simulate a shallow water gas seep at a test site near Kingston Beach, southern Tasmania. The EM2040 provides a 1.3° by 1.3° transmit and receive angular resolution respectively. Data were acquired at 300kHz frequency using single swath mode, short CW pulse, beam spacing set at equidistant and sector coverage set to 65° port and starboard (total coverage 130°). Data are stored in *.all raw format for bathymetry and backscatter and in *.wcd format for water column backscatter at the CSIRO. There are 397 *.all and 373 *.wcd files totaling 129 GB of raw multibeam data in this dataset. Sound velocity profiles were applied to the data during data acquisition. Bathymetry data contained in *.all format have been corrected for motion and position. Additional information regarding this dataset, including further information on processing streams, is contained in the GSM data acquisition and processing report (sc2020_v01_Bubble_experiments_CCS_Rev_1.pdf). Water column data were post-processed using custom MATLAB workflows. A variety of workflow methods were tested, with the processing results of each available in *.txt and *.jpg format. Additional data products may be available on request.

This record describes multibeam echosounder data collected on RV Investigator voyage IN2022_V02, titled "Sedimentation at its extreme: how powerful are submarine caldera-forming eruptions (Kermadec arc)?" The voyage took place between March 15, 2022 and April 19, 2022 (AEST), departing from Hobart and returning to Hobart. The Kongsberg EM710 MKII multibeam echosounder was used to acquire seafloor bathymetry and backscatter information and watercolumn backscatter in shallow water (<500m) on the shelf of Tasmania and a small portion of the New Zealand continental shelf. The EM710 MKII provides a 0.5° by 1° transmit and receive angular resolution respectively. The echosounder's nominal frequency range is from 40 to 100 kHz. During IN2022_V02 the frequency range was set from 70 to 100kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 37 *.all files totaling 8.15 GB of raw bathymetry/backscatter data and 31 *.wcd files totaling 48.7GB of watercolumn data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position. GPS tide was computed using the EGM2008 model and applied to the processed data. Processed data has had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format. Additional information regarding this dataset, including further information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes multibeam echosounder data collected on RV Investigator voyage IN2019_V07, 'RAN Hydrographic and Maritime Heritage Surveys' which departed Hobart on the 11 April 2019 and returned to Hobart on the 23 April 2019. The Kongsberg EM710 MKII multibeam echosounder was used to acquire seafloor bathymetry and backscatter information [and watercolumn backscatter] along the Tasmanian East coast and in the central to eastern region of Bass Strait. The EM710 MKII provides a 0.5° by 1° transmit and receive angular resolution respectively. The echosounder's nominal frequency range is from 40 to 100 kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 337 files totalling 67 GB of raw data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position. Tide corrections were applied to some of the processed data (i.e. AHO mapping area - files 0037 to 0112, and to other mapping sites - files 0188 to 0256). GPS tides (and reduction to AHD using AusGeoid 09) was applied to the BMR mapping areas (files 0257 to 0281, 0290 to 0293 & 0295 to 0300). Processed data has had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format. Additional information regarding this dataset, including further information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes multibeam echosounder data collected on RV Investigator voyage IN2022_V02, titled "Sedimentation at its extreme: how powerful are submarine caldera-forming eruptions (Kermadec arc)?" The voyage took place between March 15, 2022 and April 19, 2022 (AEST), departing from Hobart and returning to Hobart. The main area of survey was the Kermadec arc off of northern New Zealand. The Kongsberg EM122 multibeam echosounder was used to acquire seafloor bathymetry, backscatter information and watercolumn backscatter between Hobart and New Zealand and the survey areas within the Kermadec Arc region. The EM122 provides a 1 degree by 1 degree angular resolution. The echosounder's nominal frequency is 12 kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 755 *.all files totaling 49.9 GB of raw bathymetry/backscatter data and 754 *.wcd files totaling 65.6GB of watercolumn data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position. GPS tide was computed using the EGM2008 model and applied to the processed data. Processed data had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format. Additional information regarding this dataset, including information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

This record describes multibeam echosounder data collected on RV Investigator voyage IN2019_V07, 'RAN Hydrographic and Maritime Heritage Surveys' which departed Hobart on the 11 April 2019 and returned to Hobart on the 23 April 2019. The Kongsberg EM122 multibeam echosounder was used to acquire seafloor bathymetry, backscatter information [and watercolumn backscatter] along the Tasmanian East Coast/Tasman Sea. The EM122 provides a 1 degree by 1 degree angular resolution. The echosounder's nominal frequency is 12 kHz. Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 102 files totalling 3.37 GB of raw data in this dataset. Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position. Tide corrections were not applied to the processed data. Processed data had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format. Additional information regarding this dataset, including information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.