Thank you so much for the identification of the snake. Yes, you are right. My niece said it was very aggressive when they tried to push it away from the side walk with a stick. There is also a lake behind their backyard.

Since there is a nearby pond, odds favor another incounter,have an adult observe inside mouth when snake become's agitated and opens wide. Pure white linning inside mouth means Cotton Mouth Water Moccasin,highly venomous and aggressive as well. Round eye pupil means non-poisionus,ecliptical (cat eye) is dead give away as poisionus. Here are some copy and paste from an expert,more than a few things point to cotton mouth.

Though the majority of specimens are almost or even totally black, (with the exception of head and facial markings), the color pattern may consist of a brown, gray, tan, yellowish-olive or blackish ground color, which is overlaid with a series of 10–17 dark brown to almost black crossbands. These crossbands, which usually have black edges, are sometimes broken along the dorsal midline to form a series of staggered halfbands on either side of the body. These crossbands are visibly lighter in the center, almost matching the ground color, often contain irregular dark markings, and extend well down onto the ventral scales. The dorsal banding pattern fades with age, so older individuals are an almost uniform olive-brown, grayish-brown or black. The belly is white, yellowish-white or tan, marked with dark spots, and becomes darker posteriorly. The amount of dark pigment on the belly varies from virtually nothing to almost completely black. The head is a more or less uniform brown color, especially in A. p. piscivorus. Subadult specimens may exhibit the same kind of dark, parietal spots characteristic of A. contortrix, but sometimes these are still visible in adults. Eastern populations have a broad, dark, postocular stripe, bordered with pale pigment above and below, that is faint or absent in western populations. The underside of the head is generally whitish, cream or tan. When sufficiently stressed or threatened, this species engages in a characteristic threat display that includes vibrating its tail and throwing its head back with its mouth open to display the startling white interior,[17] often making a loud hiss while the neck and front part of the body are pulled into an S-shaped position.[22] Many of its common names, including "cottonmouth" and "gapper", refer to this behavior, while its habit of snapping its jaws shut when anything touches its mouth has earned it the name "trap-jaw" in some areas.[23] Other defensive responses can include flattening the body[22] and emitting a strong, pungent secretion from the anal glands located at the base of the tail.[11] This musk may be ejected in thin jets if the snake is sufficiently agitated or restrained. The smell has been likened to that of a billy goat, as well as to a genus of common flood plain weeds, Pluchea, that also have a penetrating odor.[

Thank you very much for this additional information.

Chitra

A veterinarian told me that most people & other critters who die after being bitten by a snake don't die from the venom;

they die from massive bacterial infection from the swarming microbial zoo that lives in a snake's mouth.

so even if that snake is totally venom-less...don't let it bite you!

& if a snake does bite you, no matter what kind of snake it is, get some good antibiotics from your doctor.

A lot of misinformation here that might be worth correcting:

1. Most people that are bitten by venomous snakes don't die. In fact, it is very rare for someone to die of snakebite in this country. The odds are under 1% of the bites. I personally know dozens of people who have been bitten by venomous snakes (I'm a herpetologist by training) and I know of one person who died. That person was in the mountains of Myanmar and was bitten by a highly venomous cobra and was unable to get medical help. If you are bitten in the US, you aren't going to die.

Statistically, more people are killed by dogs, horses and falling furniture every year in the than by snakes.

2. I've never heard of a single person dying from an infection derived from a snakebite. I think you vet needs to stick to the facts that they know.

3. I've been bitten by many hundreds of non-venomous snakes(and one venomous) and have never had an infection from one any more than you would get from scratching yourself on a plant while gardening. A dog or cat bite is much more serious.

4. You should never rely on the lining of the mouth to identify cottonmouths. Yes, adult cottonmouths do have a white mouth lining, but young ones generally don't. Their mouth lining is pinkish, just like many other snakes. And if you are getting close enough to a potentially dangerous snake to see the mouth color, you are putting yourself at risk.

Furthermore, cottonmouths don't always show their mouths when scared. Some do, most just try to get away.

Cottonmouths are NOT aggressive. I know this because I have done research with the species in the swamps of South Carolina (where I encountered hundreds of individuals) and have also seem many hundreds of cottonmouths in Texas during the course of my birding and herping. Cottonmouths are slow and heavy bodied. They know they aren't fast so their only defense is to sit there and hope you don't notice them. If you get to close, they will sometimes flash their mouth lining but rarely strike, even if seriously provoked.

If you want to know the truths about cottonmouths, there is a great article on Slate dispelling the myths and linking to the research - http://www.slate.com/articles/health_and_science/science/2014/09/cottonmouth_natural_history_myths_research_feeding_and_mating_habits_of.html

As for identification of cottonmouths, they can be tough to tell from harmless snakes unless you know how to identify snakes properly.

Things that DO NOT work for identification include:

1. Swimming on top of the water - sometimes cottonmouths to swim high in the water (floating on top). But they can (and do) swim underwater. And harmless snakes can swim above or below the water as well. So this "characteristic" sometimes works and sometimes is wrong. How useful an identifying character is that?

2. Have elliptical pupils (like a cat) - they do, but so do some harmless snakes. And elliptical pupils aren't always elliptical. They open up and become round in dim light, just like they do on your cat. So once again, not a safe characteristic to rely on.

3. Have triangular shaped heads - yes, they do...sort of. But many non-venomous species also triangular shaped heads or can flatten their heads out when threatened to make them look triangular. And by triangular heads on cottonmouths....do they mean seen from above or from the side? Again, not a useful character.

It isn't hard to learn to identify the venomous species that live in your area, but you should learn the characters from reliable sources like field guides, not urban legends.

Tell your niece to pick up one of these at HEB, https://www.amazon.com/Snakes-Central-Texas-Notable-Reference/dp/0982551630. It'll help for the common ones- and she's going to see quite a few living near water! Tell her to be especially careful when gardening, and make lots of noise so the snakes have time to run away.

If you're on facebook, there is a group called Snake Identification. Very, very helpful.

Well as for this "If you are bitten in the US, you aren't going to die". I disagree. I recall watching a television show a few years ago filmed inside real emergency rooms with real patients here in the united states. A man went for a walk during his lunch hour and was bitten by a rattlesnake. He immediately drove himself to an emergency room. He was given state of the art medical care, multiple infusions of anti-venom, saw half a dozen doctors, emergency medicine doctors, intensivists etc. And was dead within 24 hours. This was a grown, otherwise healthy 40 something male. 6 feet tall 200 lbs. Of course a reptile expert is going to say snakes are great don't hurt snakes. He or she thinks they're really cool. He or she is not a medical doctor. Venomous snakes are dangerous and potentially deadly. If I see a snake that might be venomous near my residence I'm killing it period. I'm not giving it the benefit of the doubt. I have a small child, pets, etc. And if there is a one in 10000 chance it could kill me, a child, or even my dog it's going to get killed. Further, you can't make broad generalizations about animal behavior like "these are not aggressive." It's an animal, it is unpredictable. Suggesting "that can't kill you because I know some people who have survived" is cavalier and wreckless advice based on andecodtal evidence from a lizard lover. I say kill the snake.