OSU is working on a new system for harnessing Poseidon's limitless energy. Their website is short on details, but the basic concept is ... well pretty basic, and you'll the get the gist from the above graphic. Pretty heady stuff.
The New York Times has an article about the technology and concerns it raises with fishermen and environmentalists. I have heard previous concepts for wave energy which center around submerged turbines which would be powered by ocean currents. That technology I could see unacceptably effecting sea-life. In fact in discussing the wave-turbines with Jes, she proposed a solution almost exactly like the illustration above.