While business competitions are increasingly on the rise in a variety of sectors, such as the Tech Challenge, which was recently covered on SocialBusiness.org, Fish 2.0 is one that stands out simply because of its particular focus.
Broadly speaking, the competition takes sustainable aquaculture businesses and fisheries and connects them with investors. If you're in one of those realms, however, you'll have to wait until the next competition gets going (assuming it does) as the deadline for the first round of Fish 2.0 was March 31, 2013. The requirements aren't as strict as some: you don'e need to have a business plan in place in order to get your hands on the $75,000 worth of prizes as well as networking opportunities.
Fish 2.0 website