Crocodylus johnsoni can reach a maximun length of three meters. It has a light brown body with darker bands on its body and tail and lighter brown bands on its snout. This creature eats fish, insects, small invertebrates, amphibians, mammals, birds, and other small vertebrates. The females nest in holes that are exposed on sandbars during the dry season from August through September. Mating occurs three to six weeks before laying.
Egg laying usually occurs at night.
Eggs are faced with predation by monitor lizards and feral pigs. The nests of eggs are left unguarded, but the mothers reappear in late October. At the end of the incubation period, the mothers carry the newly hatched young to the water in their mouths. The mothers then stay close to the young and protect them for a short period of time. This species occupies various fresh water areas such as lagoons, rivers, billabongs, and swamps.