Discover the 6 Most Dangerous Animals Lurking in Arizona’s Lakes and Rivers

Written by Angie Menjivar
Updated: April 20, 2023
© Vaclav Sebek/
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Key Points:

  • Lakes and rivers have dangers beyond animals, including boating accidents and drownings.
  • There are two dangerous creatures in lakes and rivers, including Gila monsters and quagga mussels.
  • Around lakes and rivers, you have rattlesnakes, poisonous spiders, scorpions, and javelinas.

When you’re in Arizona, there’s nothing like heading toward a water source to cool off, especially when the summer season rolls around. But, while time spent at lakes and rivers can make for great memories and great tans, there are some dangers you need to look out for to keep yourself and your loved ones safe. We don’t cover all of the dangerous (and sometimes deadly) animals in Arizona, but we do highlight the ones that lurk around Arizona’s lakes and rivers!


Are Arizona Lakes and Rivers Dangerous?

Arizona lakes and rivers can be hazardous, but not necessarily because of dangerous animals. There are several lakes where boating accidents are most prevalent, including Lake Havasu, Lake Mead, Lake Mohave, Lake Powell, and Lake Pleasant. Unfortunately, drinking and boating plays a major role in the frequency of these accidents, so it may just be that humans themselves pose the most significant risk to one another.

Another danger in lakes and rivers is the possibility of drowning. Even avid swimmers can be pulled under by a current. Additionally, some contaminants could pose a risk. For example, Oak Creek feeds the Verde River, and there’s plenty of swimming access along the way to the Salt River. There have been several issues with E. coli in Oak Creek, which poses a threat to the waters it feeds.

A List of the Most Dangerous Animals in Arizona’s Lakes and Rivers

1. Gila Monsters

Gila monsters acquired their name from where they were discovered. The Gila River Basin in Arizona is where these venomous lizards were first spotted. Although a bite from a Gila monster isn’t necessarily life-threatening, it sure is painful. The pain can be described as an intense burning that’s accompanied by dizziness, vomiting, changes to heart rate and blood pressure, and swelling. The good thing is these generally timid reptiles move slowly and don’t display aggression toward humans — unless they’re threatened.

Lizard Gila Monster( Heloderma suspectum) on sand
Gila monsters are venomous lizards among the most dangerous animals lurking in Arizona’s lakes and rivers.

©Vaclav Sebek/

2. Quagga mussels

These aquatic animals are a bit different in that the danger they pose is mostly geared toward Arizona’s native plants and animals. Originally from Eurasia, quagga mussels have found their way over to Arizona lakes and rivers. They are quite resilient, even surviving outside of water for several days. They tend to cling to boats and can even coat the entirety of a river or a lake’s floors. They’re found in different lakes like Saguaro, Canyon, and Apache. You can also find these in the Salt River.

Quagga mussels are an invasive species in Arizona’s lakes and rivers.

©Chris Dale/

Dangerous Animals Around Arizona’s Lakes and Rivers

1. Rattlesnakes

Not all dangers are inside the water; some hang out around rivers and lakes. Rattlesnakes run — well, slither — rampant throughout the state, with 15 identified species calling this state home. When the weather warms up, Arizonians and visitors head outdoors, but that’s where rattlesnakes are usually also enjoying the warm weather. If you’re headed out to hike around a lake or go boating, learn what they look like and how to identify them. If you hear rattling, retreat!

Black-tailed Rattlesnake
The Black-tailed Rattlesnake is native to Southwest Arizona.

©Joe McDonald/

2. Black Widow Spiders

Although spiders play their own role in our ecosystems, some are dangerous to humans because they’re venomous. One such spider is the black widow, which is easily recognized by its glossy black body and the tell-tale red marking on its abdomen. Although these spiders tend to mind their own business, they may be hiding in areas around lakes that you may not be watching. If their webs are disturbed, they may bite, and that bite is painful, causing lots of muscle pain and even shortness of breath.

Animals with exosceleton black widow spider
The Black Widow is a highly venomous spider.


3. Scorpions

Scorpions have been spotted in the Lake Pleasant area, and children are the most vulnerable to their stings. Adults rarely see complications, but nevertheless, deaths have occurred in all age groups. The ones around Lake Pleasant are a light orange/brown color. They get as big as three inches long and typically prefer the cover of nightfall to roam about, which makes them hard to spot. Although most scorpion stings heal without medical intervention, it’s best to get attention right away when symptoms are severe.

Arizona bark scorpion crawling down a tree
The Arizona bark scorpion is the most dangerous North American scorpion.

©Ernie Cooper/

4. Javelinas

Javelinas look a lot like pigs. They have hooves, and although they typically don’t bother humans, if they’re feeling threatened, they become a danger. If you head out with your pets, keep in mind that javelinas pose a threat not only to you but to your pets as well. A lone one may not be able to do too much damage, but these mammals travel in groups called bands. Be sure to clean up well because they’re attracted to food and garbage.

Javelinas look like pigs and can be dangerous to your pets.

©Dennis W Donohue/

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The Featured Image

Lizard Gila Monster( Heloderma suspectum) on a rock
© Vaclav Sebek/

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About the Author

Angie is a writer with over 10 years of experience developing content for product and brand reviews, focusing much of her time on animals of all types. A cat owner herself, she enjoys writing articles on beloved pets that both inform and entertain her audience.

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