The Koolasuchus are one of the largest amphibians ever at almost 5 meters long. It had a large, flat head, with nostrils at the top of its snout, and small limbs. It had a strong tail that it used to swim and hunt. It is unclear how this carnivorous animal would hunt its prey, but it is thought to have hunted by attacking it by surprise, or by sinking to the bottom of the river and eating the fish that passed by. It lived in rivers, and would walk on land occasionally; but when doing so, it was very slow and sluggish. It is unclear if it went through a metamorphosis stage like many terrestrial amphibians do, but if it did it would start from a larvae, to juvenile, and then adult.