Cottonmouth vs. Water Snakes: The Main Differences

Written by Dana Mayor
Updated: May 15, 2023
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Key Points

  • Both snakes have adapted to living in water and also bear a close resemblance to each other.
  • However being able to tell them apart is crucial since cottonmouths are extremely dangerous while water snakes are harmless.
  • The main difference lies in the shape of the head in the water moccasin vs water snake, which is large and angular for the former, and flat and round for the latter.

Cottonmouth snakes, also known as water moccasins, are incredibly venomous. Their venom can kill a human, so it’s understandable that so many people fear them — and frequently confuse harmless water snakes for the cottonmouth. However, it’s important to know the difference between the water moccasin vs water snake for your own safety, as well as the safety of harmless water snakes — who are often killed due to being confused with venomous cottonmouths! Let’s dive into what separates cottonmouth vs. water snakes!

Comparing Water Snake vs Cottonmouth

Cottonmouth vs Water Snake - Cottonmouth
A cottonmouth snake that’s ready to strike


Water snakes, especially the northern water snake, can look very similar to cottonmouths. They are both dark in color, with darker markings along their bodies.

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Water snakes may be banded like cottonmouths, or have patches that look similar to bands when observing them. Both water moccasin vs water snakes tend to stay close to fresh water sources and are found throughout the United States.

However, Cottonmouths do have some distinctive features which include a larger body and head, thin neck, distinctive eyes, and pits on the sides of their faces.

Water snakes and cottonmouths look quite similar, possibly because they’ve both adapted to survive in the water. However, they are completely different snakes and belong to different families.

In addition, it’s important to note that there are several species of water snakes, each slightly different in color and appearance.

These include:

  • Northern Water Snake: This is the most common water snake found in the United States. At five feet in size, they are the most likely to be confused with Cottonmouths. They have dark splotches on their scales, which are easily mistaken for the dark bands of a Cottonmouth. If you cannot tell the difference, it’s always best to keep your distance from these snakes rather than risk yourself by getting closer.
  • Southern Water Snake: Also known as banded water snakes, these snakes are found in the southern United States. They can be red, brown, or black in color, and are banded. Their coloration darkens as they grow older.
  • Brown Water Snake: These snakes have light brown scales with darker patches. Their head is diamond-shaped. Brown water snakes are found in the Southeast of the United States and are often seen in trees, as well as in the water.
  • Yellow-Bellied Water Snake: Just like the name suggests, these snakes have yellow undersides. The tops of their bodies are grey, green, or black. They live around the Gulf Coast.
  • Red-Bellied Water Snake: These snakes are brown or grey with bright orange to red undersides. They are found on land more often than other water snake species.
Cottonmouth vs. Water Snake - Pair of northern water snakes
A pair of northern water snakes


Water Snake Cottonmouth 
LifespanUnknown wild lifespan; up to 9 years in captivityLess than 10 years in the wild; sometimes over 20 years in captivity
HeadRounded, flat, sometimes has eye stripeLarge, square, always has eye stripe
Body Long, thin body; no noticeable neckThick body with narrow neck
PitDoes not have pitHas pit

The 5 key Differences Between Cottonmouths and Water Snakes

1.     Cottonmouths have large, chunky heads

Cottonmouth heads and necks are distinct from their bodies. While Cottonmouths have square heads, water snakes have rounded or flat heads that are not thicker than their bodies.

In addition, cottonmouths always have an eye stripe. Water snakes often have this feature as well, but not always.

2.     Watersnakes are thinner with no defined neck

Water snake bodies are long and muscular, but not thin. Their head is not distinct from their body, so they have no defined neck.

Cottonmouths, on the other hand, are much thicker and heavier snakes. They also have big, blocky heads that stand apart from their bodies, creating a distinctive neck.

Cottonmouth vs Water Snake - Water snake on a branch
A water snake on a branch

©Katie Flenker/

3.     Cottonmouths have Oval Pupils

Cottonmouths have oval, slit-like pupils — similar to that of a cat. Water snakes have circular pupils.

It is also worth noting that the eyes of cottonmouth snakes cannot be seen when observing them from above.

Those of water snakes on the other hand are visible when you look down at their heads.

4.     Water Snakes do not Have Pits

Cottonmouth snakes have pits on each side of their head, between their eyes and nostrils. These pits sense heat, allowing the snakes to detect and strike down prey.

Water snakes do not have these pits.

However, by the time you see if a snake has pits or not, you’re often too close for comfort! So, this isn’t a super reliable way for the common person to distinguish between these snakes.

Cottonmouth vs. Water Snake - Cottonmouth Biting
A cottonmouth snake showing its fangs

©Seth LaGrange/

5.     Cottonmouths Live Longer

Lastly, let’s consider the longevity of a water moccasin vs water snake. Cottonmouths can live about twice as long as water snakes in captivity. Some cottonmouths have lived over 20 years, though their lifespan in the wild is much shorter.

Captive water snakes only live up to 9-10 years. Though we don’t know their average wild lifespan, we can guess that it’s similarly short. Animals rarely live longer lives in the wild than they do in captivity.

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I love good books and the occasional cartoon. I am also endlessly intrigued with the beauty of nature and find hummingbirds, puppies, and marine wildlife to be the most magical creatures of all.

FAQs (Frequently Asked Questions) 

What Should You do if You’re Bitten by a Snake?

If you’re bitten by a snake, you should always seek medical care right away—particularly if you’re unsure whether or not the snake was venomous.

Even water snake bites should be watched for signs of infection such as swelling, discoloration, or failure to heal.


Can a Cottonmouth Kill a Human?

Yes, Cottonmouth venom can kill a human—but it’s not likely. While it’s rare to be bitten by one of these snakes, it’s definitely not something you should risk!

If you are bitten, though, you shouldn’t panic. Thousands of people are bitten by venomous snakes every year in the United States, but only a handful end up dying from the bite.

You’re more likely to experience symptoms such as pain, nausea, numbness, trouble breathing, poor vision, or an increased heart rate.

Will a Cottonmouth Snake Chase You?

If you encounter a wild cottonmouth (or any wild snake), you should calmly back away from the area. Cottonmouths don’t tend to be aggressive. Although they will lash out and bite in fear, they will not chase you.



Should I Kill Cottonmouth Snakes?

No, you should not try to kill Cottonmouths. You’re much more likely to be bitten if you try to kill these snakes than if you simply leave them alone.

It may also be illegal to kill Cottonmouths in your state.

Do Water Snakes or Cottonmouths Make Good Pets?

No. Water snakes are very aggressive animals, despite lacking venom. Though Cottonmouths are less aggressive, their venom makes them dangerous to keep.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.