Tidal Power

This article is about an investor who gave $2.6 million to Hydro Green Energy to fund their research in using tides to create electricity. When reading this article, I couldn't help but wonder how much money will it cost to build these large plants? This article was in the "green" section, but in the article it states the effect on marine life is unknown. Are we creating a bigger problem by spending $$ and putting the future of marine life at risk?

http://www.news.com/8301-11128_3-9920651-54.html?tag=cd.blog