What are Water Snakes?

Brendan McGuigan

Water snakes are any of a large number of snakes found throughout the world that swim and hunt in the water. Although most species are not poisonous, those that are include some of the most deadly snakes known. For this reason, care should be taken when faced with an unknown water snake.

Water moccasins are venomous snakes found near the water, especially in the southern United States.
Water moccasins are venomous snakes found near the water, especially in the southern United States.

Although all snakes can swim, some are particularly at home in the water. These snakes, which include cottonmouths, Northern water snakes, Asiatic water snakes, Rainbow water snakes, and mangrove snakes, can be very dangerous for unaware bathers or swimmers. At the same time, these snakes have nothing to propel off of, making their strikes much slower.

Giant otters prey on water snakes in the Amazon.
Giant otters prey on water snakes in the Amazon.

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Most snakes, even water snakes, are simply not as effective in combat when not on land. For this reason, they will tend to not attack unless provoked, and for the most part, snakes in the water will run away rather than fight. That said, if a snake feels threatened or cornered, or is accidentally jarred, it will likely lash out.

The best thing to do to avoid undesired encounters with water snakes is to stay away from places where they like to sun themselves. Primarily, this means overhanging tree branches. Many snakes sit the branches to gather sunlight, and then drop down into the water if they detect motion. They’re not dropping to attack — they’re actually trying to run away — but if they happen to land in a boat or on a swimmer, they can panic and attack.

In North America, only one species is poisonous: the cottonmouth water moccasin. Water moccasins are related to rattlesnakes and copperheads, and can be deadly. They have trapjaws that can snap shut quickly and with great force, driving its venomous fangs deep into flesh. Their name derives from their habit of lying with their mouths open, showing the white interiors. Although often maligned as being aggressive, water moccasins are actually fairly docile. Generally, they will avoid humans, unless provoked in some way.

A number of non-poisonous water snakes live in North America as well. These include the Florida green water snake, the diamondback water snake, the brown water snake, the salt marsh snake, the plainbelly water snake, and the southern banded water snake. None of these snakes are aggressive or poisonous, but as a number of them are at least somewhat similar in appearance to water moccasins, care should be taken anyway, unless identification is certain.

In South America, one of the most common water snakes is the mangrove snake from Venezuela and the islands of Trinidad, Tobago, and the Guianas. Although not poisonous, they are fairly easily provoked, and their bite is painful and can cause infection. The Asiatic water snake, found throughout South-East Asia, China, Indonesia, and parts of Western Asia, is another non-venomous water snake. It is quite docile, and will rarely attack unless extremely provoked.

Although not poisonous, a bite from a water snake can be painful and cause infection.
Although not poisonous, a bite from a water snake can be painful and cause infection.

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Discussion Comments


@ Anon26032- Water snakes can come from all of the families of snake listed by Georgesplane. Desert dwelling snakes can also come from all of these families except the hydrophiidae. Very few of the vipers snakes found in the United States feel at home in the water, and none are true water snakes. Only the sea snakes will regularly stray far from land and spend most of their lives in and under water.

Like the article said, not all water snakes are non-venomous. Additionally, not all desert snakes are venomous. I live in Arizona, and of all the species of snake that live here, only about thirteen are venomous snakes from the viperidae family.


@ anon26032- Whether a snake is venomous does not really have anything to do with where they live. It has more to do with the family the snake belongs. There are five major biological families that almost all snakes belong to: Colubridae, Boidae, Elapidae, Viperidea, Hydrophidiiae.

All snakes in the viperidae and elapidae families produce venom highly toxic to humans. Examples of Viperidae and Elapidae include rattlesnakes, fer de lance vipers, water mocassin, coral snakes, mambas, and cobras. Most hydrophidiiae produce venom toxic to humans. This family includes all of the sea snakes. All snakes from the Boidae family are constrictors, and include snakes like the anaconda, rock python, and boa constrictor. Of the colubridaes, most produce venom, but it is only slightly toxic to humans, posing no real risk. This family includes garter snakes, lyres, and most other known snake species.


Why are water snakes not poisonous? Why are desert snakes poisonous?

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