The swamp womp rat, also called a "swamp womper", was a variety of womp rat found on Cularin and a few fringe worlds, where they were considered a nuisance. They had muddy brown fur and long whiskers, and lived in swamps and bogs. Swamp womp rats were ambush predators, and attacked in large packs numbering up to a dozen. When they detected prey, they would swarm savagely over them, overwhelming them with numbers and trying to drag them under the water. They were skittish creatures, and would back down from dangerous creatures or surprising lights and noises.

A swamp womp rat had poor eyesight, but an excellent sense of smell. Also, their whiskers were highly sensitive sensory organs, detecting vibrations up to 20 meters away when out of water, and they could feel the vibrations of movement through the water. This sense was so acute, in fact, that they could sense repulsorlift vehicles traveling over the water within 50 meters. Not bright creatures, the rats would attack vehicles moving in or above the water. On Cularin, brave young Tarasin with access to high technology would exploit this fact, hunting them on repulsorlift vehicles. They would wait for the rats to attack and then make a fast retreat at the last second, killing one or two of them during the attack.

Swamp womp rats generally spent all their time in the water, with just their noses sticking out. They were very reluctant to come onto land, where they were vulnerable, but would do so when chasing prey or if they were very desperate.