Marine energy (or ocean energy) encompasses wave, tidal stream, tidal range, ocean thermal, ocean current, run-of-river, and salinity, etc., through which energy can be harnessed from oceans. Oceans are the source of enormous untapped energy that is accessible to most coastal countries. The estimated marine energy potential is 32 PWh/y; however, only a minor quantity is harvested worldwide. At present, global marine energy generation capacity is only 500 MW, most of which comes from tidal range (495 MW) along with a small portion from tidal stream (11 MW) and wave (2 MW) (WEC, 2016). Fig. 1.5 shows the global marine energy capacity from 2009 to 2016 (MW) (Sattista, 2017).