Big Blue was supposedly a prehistoric plesiosaur that lived in a lake in Georgia. There were numerous legends, sightings, and gift shops relating to the monster, but they began to be taken seriously following the deaths of several people on the lake. FBI Special Agents Fox Mulder and Dana Scully were brought in to investigate. Much to the chagrin of Mulder, Big Blue turned out be a very large alligator that he, himself, shot dead...or so he and Scully thought - apparently, Big Blue was real, only to go unseen, as Mulder and Scully turned away before they could see a large lake creature emerge from the water and dive down again. (TXF: "Quagmire")