Former springs and sinkholes, blue holes formed when the rising water table made Florida smaller. There are at least a dozen on Florida's continental shelf, with some plunging hundreds of feet deeper than the hard limestone floor of the Gulf of Mexico. In partnership with Mote Marine Laboratory in Sarasota, In Focus embarked on the first organized scientific investigation into the blue holes of the Gulf, exploring the plant and animal life that thrive at these extreme depths. Watch the above video.