False water cobras grow to an impressive size and are one of the larger snakes found in South American floodplains. They are a diurnal species and can be considerably active throughout the day where they climb, burrow and swim. The most common name for this snake in its native range is ñacaniná (niyah-kah-nee-nah), which originates from the Guaraní people who inhabit Brazil, Paraguay, Bolivia and northern Argentina.

The false water cobra is named for its ability to flatten its neck to appear larger. This gives the snake the appearance of a cobra. However, unlike a true cobra, the false water cobra does not prop itself up vertically but maintains a horizontal position. This species can also flatten other areas of its body, while a true cobra cannot. 

These snakes are venomous, but the toxicity of their venom has not been thoroughly studied. If the human body is exposed to large enough quantities, the venom can inhibit blood clotting, cause swelling and create quite a bit of discomfort. The false water cobra does not have an injecting apparatus, as some snakes with fangs at the front of their mouths do. Instead, its fangs are located at the back of its mouth, and it has to chew its prey to inject its toxin.

The false water cobra is also lacking a large venom gland. Instead, it has a Duvernoy's gland, which is found in many rear-fanged snakes and is separate from the salivary gland. As such, saliva from these snakes is not toxic, but secretions from the Duvernoy's gland are. Because of these characteristics, when fending off predators or displaying aggression, adult false water cobras generally do not attempt to envenomate but instead bite with a slashing motion to inflict a wound.

The semi-aquatic false water cobra grows to an impressive size.

The false water cobra is a neotropical snake found in southern Brazil, eastern Bolivia, Paraguay and northern Argentina. It is a terrestrial or semi-aquatic snake found in wet, tropical and humid habitats, often near streams or in the floodplains of rivers.

The false water cobra's size, abundance within its range and generalist diet make it an important predator in the region it inhabits. This snake feeds primarily on tadpoles, fish, frogs and other aquatic amphibians. It also eats reptiles, mammals and birds found in wetland habitats.  False water cobras are voracious, aggressive predators. They hunt by grabbing and partially coiling their bodies around their prey, then swallowing it live. 

Male false water cobras are sexually active year-round, while females vary from annual to seasonal. Larger females are more likely to produce more offspring. These snakes are prolific breeders, regularly producing two egg clutches per year. The clutch size averages 14 to 24 eggs, but clutches as large as 36 eggs are not uncommon. Eggs typically hatch after about 60 days at an incubation temperature of 83 degrees Fahrenheit (28 degrees Celsius). Hatchlings measure about 38 centimeters (15 inches). Hatchling and juvenile false water cobras are darker in coloration and lack the dark eyes of adults; their appearance has been compared to that of a garter or water snake.

Like other neotropical snakes, false water cobras are understudied, and further research is need to understand their natural history and full ecological significance. What is known about this snake is that it is an important predator in its native wetlands, helping to keep populations of other species in check.

These wetlands were once home to apex predators, such as jaguars and giant Brazilian otters, that also fulfilled this function. However, those animals are either locally extinct in certain regions or greatly reduced in numbers due to human activity. A better understanding of false water cobras could help protect the species and its habitat.