Wels catfish are freshwater fish with razor-sharp teeth that can grow up to 16 feet in length!

You can find Wels catfish in rivers and lakes throughout Europe. They are easy to spot with their huge mouths and broad, flat heads. They'll eat just about anything, including frogs, rodents, fish, insects, worms, and birds.

Some have been known to attack humans and even go as far as killing them! Typically these people are unsuspecting swimmers or fishermen.

While boxfish are similar to pufferfish in many ways, they aren't as dangerous.

However, these poisonous fish still shouldn't be reckoned with.

Boxfish grow anywhere from 10 to 24 inches in length and can be found throughout the Pacific, Atlantic, and Indian Oceans.

With honeycomb skin patterns and box-shaped bodies, they are pretty easy to identify.

Boxfish release ostracitoxin through their skin, surrounding the water and poisoning 

The puffer fish might be one of the most dangerous fish in the world. We know of more than 120 pufferfish species, some of which are only an inch long, while others can grow more than two feet.

You can find these poisonous fish in tropical and subtropical waters worldwide. Hence the name, they will inflate into large balls when they feel disturbed or threatened. Their large spines become instantly visible when puffed up, making them all the more terrifying.

Within their liver, intestines, and ovaries, they carry a powerful poison known as tetrodotoxin. 

There are more than 200 species of moray eels in the ocean, though some moray eel species live in freshwater.

Many people mistake these eels for snakes, as they don't have any pectoral fins. They often attack divers, hopping out of rocky crevices when accidentally disturbed. They often live in shallow waters.

The moray eel has wildly sharp teeth with an angled design that prevents prey from 

You can find the oceanic whitetip shark in tropical seas around the world. Though tiger sharks, bull sharks, and great white sharks attack humans more than oceanic whitetips, there are more recorded deaths from this species.

One of the most famous ocean whitetip shark attacks was when the USS Indianapolis was sunk by a Japanese submarine on July 30,  

The lionfish is an incredibly venomous fish found throughout the Pacific Ocean. These fish can reach up to 18 inches long and are easy to spot, thanks to their bright colors.

Lionfish have black, red, or white bands and venomous fin spines that they use to attack their prey. However, they'll also often use their mouths to blow out small jets of water, confusing their prey before attacking them.

The sting of a lionfish can cause serious pain, breathing difficulties, and vomiting. While they aren't fatal in most cases, they can be extremely dangerous for children and the elderly.

The stonefish is the most venomous marine animal and the most dangerous fish in the world. These bottom-dwelling fish grow from around 14 to 20 inches long and have extremely wide pectoral fins. You can find them in tropical waters throughout the Pacific Ocean, Indian Ocean, Great Barrier Reef, and Red Sea.

With razor-like spines and crusty skin, they give off toxins that can kill a healthy adult in less than an hour. What makes the most venomous marine animal even scarier is that it can camouflage itself by sticking to the seafloor 

Candiru might be small at about one inch long, though they are an extremely dangerous species that you should do your best to avoid. These dangerous fish live in the freshwater regions of the Amazon Basin, though they can be nearly impossible to spot due to their translucent bodies.

They are parasitic, often living inside the gills of

The Goliath Tigerfish is easily the most dangerous fish on the African continent.

You can find this well-known species throughout the Congo River basin, feeding on just about anything they can wrap their mouths around.

They are highly predatory fish with very sharp teeth that protrude from their mouths, very similar to Piranha. Each of their teeth can grow up to an inch long!

You've likely heard of the electric eel before. This unique eel, native to South America, can produce a painful electric shock to stun its prey.

If its electric shock capabilities aren't enough to make you squirm, the electric eel can grow up to nine feet long!

While the box jellyfish is an invertebrate, and not actually a fish, their incredible power gives them a warranted spot on this list. Plus, many people think of them as the most dangerous fish in the world. These extremely venomous marine animals contain poison that can kill a human in a matter of minutes. If you don't die from a box jellyfish sting, the marks it leaves on your skin can last lifetime.

Some of the side effects of a box jelly sting include low heart rate and a "sense of impending doom."

Box jellies can be found in waters near Japan, Mexico, and Australia.