An assorted collection of wave and tidal power devices is to be deployed off the coasts of Scotland within the next ten years, demonstrating that there is a choice of technologies available to harness marine energy, but also that we aren't quite sure yet which of these technologies is going to be the most efficient one in practice.
I wrote a news feature about this for Current Biology, which came out last week while I was away and offline:
Wave power set to roll
Current Biology, Volume 20, Issue 7, R299-R300, 13 April 2010
summary and limited access to pdf file