There are many ways to harness the renewable and emissions-free energy available from the Earth's oceans. The technologies include wave energy, tidal and current energy, and energy from thermal and salinity gradients. In addition, offshore wind energy and marine (floating) solar arrays offer a possibility to exploit vast resources that are far larger than those available onshore. The potential capacities range from many hundreds of gigawatts to terawatts of generation. These technologies could contribute a significant part of the global electricity demand; they are particularly suitable for providing sustainable power to marine regions and island communities and nations. This book brings together contributions from international experts with academic and industry backgrounds to provide a systematic overview of ocean energy technologies, their readiness and modelling, as well as installation and grid connection technologies.