In Australia you have the Yowie and the Bunyip. Wyverns were reputedly swam dwellers as were some mermaids (Mangrove swamps there) and I think the Hydra was also a Swamp dwelling monster (could be wrong there.) Hope that helps. read more
Vampires are reanimated human corpses, although some may argue that they aren't"mythical" creatures. The Draugar (singular: Draugr) of Scandinavian lore can shapeshift; they, too, are undead men. Werewolves are humans with mutations. read more
Swamp monsters in folklore, legends, and mythology. The Will-o'-the-wisp appears in swamps, and in some areas there are legends of it being an evil spirit. The Bunyip are a creature from Aboriginal mythology that lurk in swamps, billabongs, creeks, riverbeds, and waterholes. read more