Lizardfolk
Lizardfolk are what you fight in a swamp. If you are in a swamp, you will probably fight lizardfolk. Swamp=Fight lizardfolk. Considering how amazing and how variable/awesome lizards are in the real world it's sad that this is all RPGs offer (especially since swamp reptiles are usually crocodilians, snakes, or turtles, rather than lizards).
Despite their mutual reptilian looks, lizardfolk are quite distinct from and not related to Dragons, Dragonborn and Draconians. This is probably because the ancestors of dinosaurs and modern reptiles diverged from each other roughly 285 million years ago during the Early Permian epoch.