The global need to diversify energy portfolios, expand renewable energy supplies and reduce carbon emissions, has motivated research and development (R&D) of marine and hydrokinetic (MHK) energy generation technologies that can capture and convert the energy contained in ocean waves, tidal and ocean currents, and offshore wind into usable energy streams or storage. This presentation reviews the opportunities and challenges for advancing these technologies globally and efforts by the US Department of Energy’s (USDOE) Water Power Technologies Office and the National Laboratories to support this emergent renewable energy industry. Specific projects that are highlighted include: 1) The reference model project (RMP) that disseminates detailed open-source non-proprietary MHK technology designs for research, and estimates of annual energy production (AEP) and costs for initial benchmarking of levelized costs of energy (LCOE); 2) The development of open-source modeling tools, e.g., CACTUS, for the design and analysis of MHK technologies; 3) The creation of resource atlases, including maps and databases that provide critical data inputs on resource attributes and extreme load conditions to support siting, technology design, project development and regional energy planning.