The National Marine Sediments Database and Seafloor Characteristics project is a collaborative effort between the National Oceans Office and Geoscience Australia. The aims of the project included identification and collation of existing marine sediment data within the Australian Marine Jurisdiction, development and population of the MARS sediments database and mapping and analysis of sediment data for the Northern Planning Area and the Australian region to provide information for the National Benthic Marine Bioregionalisation. The creation of the MARS database marks the transition to a new era of easy internet access to quantitative seafloor information. This is the first project to critically assess the quality and coverage of Australia's seafloor sediment data on a national scale. The initial phase of the project was the identification and collation of sediment data. At the completion of this phase, the MARS database contained about 25,000 samples for which 138,000 properties had been recorded. Maps of sediment properties were produced using validated quantitative data for two regions: the Northern Planning Area (NPA) and the whole of the Australian Marine Jurisdiction, excluding external territories. These maps show the distribution of measured grain size data (weight percent gravel, sand and mud), calculated mean grain size, as well as sediment classification based on the Folk scheme (Folk, 1954), and carbonate content. Mean grain size data for six of the marine domains were used to model sediment mobility in waters less than 300 m depth, using Geoscience Australia's GEOMAT package. The results of the modelling were produced as maps of tide and wave exceedance, and an energy regime regionalisation. As a direct result of this project, the MARS database is now an important scientific and educational resource for those requiring detailed information on seafloor sediment characteristics within the Australian Marine Domain areas. The maps generated by this project show the level of detail and type of presentation possible when using quantitative data, but significant gaps in measured data coverage were also identified. Some 70% of the total marine domain remains unmapped in terms of measured sediment data. Much of this area is off the continental shelf, although gaps in the data coverage on the shelf are significant, particularly in the South-west and West-central Marine Domains Strategic directions for improving the data coverage include the analysis of existing sediment samples from Australian and overseas repositories. A valuable resource of seabed samples stored in Australia and overseas has been identified. These samples, if analysed, have the potential to double the existing overall measured data coverage for Australia's Marine Domains and would provide a cost-effective way of generating new data. The South-west Marine Domain would provide a useful pilot study to test the utility of analysing existing material.