According to the Lost Tapes site on Animal Planet, the Swamp Creature "is said to be covered in a thick coat of matted gray or brown hair. Its yellow eyes are seemingly reptilian, and the smell it emits has been called the stench of death. This primitive creature has long been blamed for the deaths of livestock and the mysterious disappearances of children in adjacent areas."
The Swamp Creature only attacks if something or someone where to disturb its nest (or eggs). In Lost Tapes, the professor's nephew Ethan had stepped on one of its eggs, thus the Swamp Creature pursued them for revenge. Fortunately, no one was killed, but Bud Ray (the fisherman) was injured but resumed to fish. It is mentioned that from then on he does not wander off in the swamp at night.