Here's an interesting idea being studied in Maine: A wave powered generator, with no moving parts.
Moving parts and the ocean aren't a good mix. This idea (video below), may make it to a full sized generator in a few years. A full sized rig would be about 100' long and tethered to the seabed.
http://www.bloomberg.com/news/articles/2016-04-12/this-device-could-provide-a-third-of-america-s-power