The Asian swamp eel has a scaleless, anguilliform body that grows to a meter or less, typically 25 to 40 cm as an adult. As a swamp eel, it has a tapering tail and blunt snout, and lacks pectoral and pelvic fins. The dorsal, anal, and caudal fins are rudimentary, with the caudal fin often absent. These fins serve to protect the swamp eel against rolling, and assist in sudden turns and stops. Its gill membranes are fused, but one v-shaped gill is located beneath the head. Such a shape prevents reverse flow.