Renewable energies play a fundamental role within the current political and social framework for minimizing the impacts of climate change. The ocean has a vast potential for generating energy and therefore, the marine renewable energies are included in the Sustainable Development Goals (SDGs). These energies include wave, tidal, marine currents, ocean thermal, and osmotic. Moreover, it can also be included wind, solar, geothermal and biomass powers, which their main use is onshore, but in the near future their use at sea may be considered. The manuscript starts with a state-of-the-art review of the abovementioned marine renewable energy resources worldwide. The paper continues with a case study focused on the Spanish coast, divided into six regions: (I) Cantabrian, (II) Galician, (III) South Atlantic, (IV) Canary Islands, (V) Southern Mediterranean, and (VI) Northern Mediterranean. The results show that: (1) areas I and II are suitable for offshore wind, wave and biomass; (2) areas III and V are suitable for offshore wind, marine current and offshore solar; area IV is suitable for offshore wind, ocean wave and offshore solar; (3) and area VI is suitable for offshore wind, osmotic and offshore solar. This analysis can help politicians and technicians to plan the use of these resources in Spain. the short and medium term, the high capital cost in the first project of each technology, the lack of experience and environmental aspects, etc. These barriers are smaller or larger depending on each of the oceanic technologies and its current development stage.In recent years, this industry has seen encouraging signs, with some of the technologies showing significant progress. This is the case for offshore wind and tidal energy, which can be considered mature enough to be ready for their commercial development. Regardless, other technologies follow a slower learning curve. Based on this, the forecasts in the short, medium, and long term are not ambitious at all [2]. With the objective of promoting the sector, various initiatives have emerged to take advantage of its energetic potential. One of them is the Implementation Agreement of Oceanic Energy Systems (IEA-OES), which aims to have installed 337 GW of capacity worldwide in 2050, objective difficult to be achieved with current figures.Another key aspect in the development of this type of project is the Levelized Cost of Electricity (LCOE) [3]. LCOE value is very high in the case of prototype projects, having a lot of room for improvement. It is important to take into account that the energy generated must have a competitive cost [4]. On the other hand, the use of green energy has other benefits. In fact, governments must support this type of project with some incentives to help the companies involved, above all in the early stages of the development of those technologies. On the other hand, a better perception of the citizens about marine renewable energy is essential, because nowadays there is a great ignorance of the possibilities of the ocean to offer clean and endles...

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