This report describes the development of four Marine Energy Conversion (MEC) technology Reference Models for producing renewable electricity from water currents (tidal, open-ocean, and river) and waves. Each Reference Model is a “point design,” a term used to emphasize that it is a unique device designed for a reference resource site modeled after an actual site in the United States. The Reference Models served as non-proprietary open-source study objects for technical and economic evaluation; specifically, they allowed the benchmarking of technical and economic performance, the collection of experimental data sets for validating open-source design tools, and the identification of cost reduction pathways and research priorities for improving performance and reducing costs. The levelized cost of energy (LCOE), in dollars per kilowatthour ($/kWh), was estimated for each Reference Model, including LCOE for a single device and arrays of 10, 50, and 100 units in order to quantify cost reductions associated with economies of scale. The Reference Models also facilitated the development of an open-source methodology for the design, analysis, and economic evaluation of MEC technologies. This project is sponsored by the U.S. Department of Energy’s (DOE) Wind and Water Power Technologies Program, within the Office of Energy Efficiency & Renewable Energy (EERE). Sandia National Laboratories, the lead in this effort, collaborated with partners from National Laboratories, industry, and universities to design the four open-source MEC Reference Models (RM1–RM4). The methodology was applied to identify key cost drivers and to estimate LCOE. Many costs are difficult to estimate at this time due to the lack of operational experience, particularly for the RM3 wave energy conversion (WEC) device.