The term 'Swamp Beastie' is a colloquial name for the crocodilian species found in swamps and wetlands. The crossword solution for this term is CROC, which is a four-letter word. Crocodilians are large reptiles that have been around since the time of the dinosaurs and are found in tropical and subtropical regions around the world. They are known for their powerful jaws and sharp teeth, and they are often feared by humans due to their size and aggressive behavior.