20 Dangerous Sea Creatures You Won’t Believe Exist

Have any of you ever gone for a swim in the ocean fearing a shark attack? This is a very common phobia; after all, sharks are often regarded as the most dangerous predators underwater. However, the sea hides plenty of tenebrous secrets, since there are many different creatures that are even more threatening for humans than sharks. And in fact, many of these creatures actually look quite innocent, and in some cases even beautiful! Here is a list of the 20 most dangerous sea creatures that you may want to admire from a distance. Don’t miss #18, #7 and #1, they’re truly amazing!

#20. TheTitan Triggerfish

If you are diving in the coasts located in between Austalia and Thailand, it’s better to be cautious of the Titan Triggerfish, which are always lurking around the coral reefs. They are often marked by lines and spots and they live in tropical and subtropical oceans. The most dangerous species from this family is the Stone Triggerfish that can reach almost one meter long.

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If you come close to one of them, we recommend you to move away and watch them from the distance! Triggerfish can sometimes be aggressive when they guard their eggs, especially if they see a scuba diver exploring their territory. Triggerfish are usually hostile towards divers and see them as a threat, that’s why they use their powerful teeth to protect their home.

#19. Stingray

Probably many of you remember the world-famous “Crocodile Hunter” Steve Irwin, one of the most adventurous men from these past years. He became famous for swimming with ferocious crocodiles, but in case you didn’t know, he was actually this killed by an Australian bull ray called Stingray. If you go to an aquarium most of them are quiet and nice, but when they’re out in the sea, they can attack other creatures if they feel in danger, including humans.

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If you are a frequent scuba diver, you shouldn’t worry too much, because the chances of getting attacked by a stingray are minimal. They don’t usually attack divers or swimmers, but if by accident someone steps on it, they will probably sting you and release a very strong venom. Injuries caused by a Stingray can be really painful and even fatal. Keep on reading the most incredible and dangerous sea creatures around the world!

#18. Flower Urchin

Flower Urchins look really beautiful and even its name is adorable but if you are ever close to one, please swim away! This animal was considered in the 2014 Guinness Book Of Records as “The Most Dangerous Sea Urchin” and not without a reason. Every “flower” that you see is actually a tentacle with a little jaw called pedicellaria. If you happen to be diving near a coral reef in the Indian or Pacific Coast, watch out for them and try to avoid them at all cost!

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It’s considered one of the most dangerous sea creatures because it’s capable of delivering extreme pain that may cause you paralysis, sometimes even leading to death. So be careful if you are diving and pay attention because flower urchins come in different colors, like pink and white or yellow and white.

#17. Electric Eel

The Electric Eel is a South American electric fish and it has some pretty unique features. To be precise, it’s not an eel but a knifefish. Their name comes from the way in which they attack and kill their predators. The Electric Eel has three pairs of abdominal organs that produce electricity and they have the capacity of producing two types of discharges: low voltage and high voltage.

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If the Electric Eel feels in danger, it will use their electricity and discharge volts towards everything they deem dangerous, and this includes humans too. However, some people have managed to capture electric eels without having received electricity, but if you ever encounter one, don’t count on your luck because the odds are grim. If you want to see one for yourself, visit the Tennessee Aquarium, which is one of the few American aquariums that have specimens of this creature.

#16. Textile Cone Snail

I bet that many of you love to collect shells when going for a walk along the beach. But next time you do that, you should bear in mind that one of the most dangerous sea animals looks exactly like a shell, but it’s secretly not. So don’t fool yourself by the way the Textile Cone Snails look. They are one of the most dangerous sea creatures found off the coasts of the Indian Ocean, the Pacific, the Caribbean Sea, and even the coasts of Florida!

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Cone Snails may look quite innocent – in fact, they’re only 10 to 15 cm long – but one single drop of their venom through a bite from their teeth can be mortal. In fact, it is said that only one drop of their venom can kill 20 men in a row! Their nickname is “cigarette snail” because when a Cone Snails bites you, you will only have enough time to smoke a cigarette before you pass away. How scary is that?

#15. Blue-Ringed Octopus

Some of the most dangerous predators are not big nor full of sharp teeth; on the contrary, many of them are smaller than a candy bar and weigh less than half a kilo, like the Blue-Ringed Octopus. At first sight, this sea creature is exquisite because of its vibrant colors and shape but it contains enough poison to kill over 20 humans in just a few minutes! So if you ever see one of them, escape immediately!

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According to Ocean Conservancy, the Blue-ringed Octopus‘ poison is capable of paralyzing anything or anyone and it’s more powerful than cyanide. But here’s some good news: they avoid confrontation with humans unless they are provoked, such as if someone tries to touch or step on them. In addition, there is no effective antidote to its poison yet!

#14. Dubois Sea Snake

We know that land snakes are scary for some people, but what about sea snakes? They must be really terrifying since it’s harder to escape from them! There are more than 50 different species of sea snakes, and most of them live in the tropical waters of the Pacific and Indian Oceans. Nothing compares to the Dubois Se Snake, however. This Australian sea snake lives 80 meters beneath the surface in coral reefs as well as in sandy and silty sediments.

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These snakes feed on moray eels and some fishes that live close to them and they are considered one of the most venomous snakes in the world and the most venomous sea snake. For nature, they are not aggressive animals but one drop of their venom is enough toxic to kill more or less 8 humans, so try to avoid them even if they hide from you. Remember, it is always better watching than touching under the sea!

#13. Pufferfish

Maybe we remember the episode of The Simpsons where the family goes to a sushi restaurant and Homer tries the most exotic plate of the place. Do you remember which animal it was? That’s right, we are referring to the Pufferfish. This inflated fish is considered a delicacy in Japan, where a group of chefs is trained each year in order to be able to prepare it. Because one wrong cut can mean the end of your life!

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This variety of fish is considered as one of the most toxic vertebrates in the world as many of their organs contain a strong poison, even stronger than cyanide. Their inflated body is the first and most important defense against predators. We know they can look really innocent and even delicious, but remember that you must only taste them in special restaurants with highly trained chefs!

#12. Box Jellyfish

Thanks to Finding Nemo, the famous Pixar animated film, we are familiar with lots of rare marine creatures. That’s why it’s not a surprise to us that Box Jellyfish is considered one of the most dangerous sea creatures under the sea, despite not having any teeth or claws! Most of them are located in Australia and the Box Jellyfish’s venom is so powerful that they can kill any sea creature that is around them. Not for nothing, Dory got really injured after crossing a wall of jellyfish!

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If you’re stung by a box jellyfish, the symptoms can be from a weak pain to heart failure. Their transparent and pale blue color makes them almost invisible to human eyes. What is scary about these creatures is that their venom has an effect in less than 5 minutes. They also have the ability to swim and have clusters of eyes on each side of their box-shaped body, so stay away from them if you ever see a group of pale blue jellyfish nearby. 

#11. Stonefish

Some animals from this list are among the most exotic and strange sea creatures that you can read about, and this is the case of the Stonefish. The more than 10 venomous dorsal spines that this fish has makes it one of the most dangerous creatures under the sea, and apart from that, their camouflaged body makes them look like another rock under the sea.

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Most of the Stonefishes are located in the region of the Indo-Pacific Coast and they’re no longer than 30 or 40 centimeters. Their poison is so effective that they can cause excruciating pain, temporary paralysis and sometimes heart failure. There is an antidote but fortunately, these fishes won’t attack you unless they feel in danger because they only use their poison as a defense mechanism.

#10. Lionfish

Their name comes from the impressive dorsal spines that make it look like a lion. Lionfish may look adorable for a pet but touching them could generate intense pains, even though they generally won’t kill you. Their spines contain a powerful venom that can sometimes cause respiratory failure and in extreme cases, a complete paralysis.

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Like we said before, it is better to just watch and not touch marine life if you go diving because most of the animals from this list use their fatal poisons to protect themselves. The Lionfish, for instance, is not aggressive and will only use their gruesome stings for own defense. You can find them in the Caribbean or in the Eastern Atlantics. What other amazing but dangerous creatures live under the sea? Keep on reading our list!

#9. Flamboyant Cuttlefish

The Flamboyant Cuttlefish inhabits on the tropical Indo-Pacific waters of Australia and New Guinea. It’s known for being the only species of cuttlefish to be toxic. Their colors are just as vibrant and exquisite as the Blue-ringed Octopus’, and both creatures are just as poisonous. Some scientists say that the flesh of these animals contains a unique toxic acid. Now you know, don’t ever try to touch one of them!

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Marine biologists agree that the colors of the Flamboyant Cuttlefish and the Blue-ringed Octopus are so bright because they want to warn predators not to bother them. Although these type of cuttlefish are one of the most dangerous creatures under the sea, you can see them in many aquariums, like the Monterey Bay Aquarium in California.

#8. Sea Slugs

As many creatures from this list, Sea Slugs are beautiful as long as you only look at them. There is an enormous variety of sea slugs, and they come in different colors, sizes, and body shapes. They have small razor-sharp teeth known as radulas. Recent studies from the University Of Queensland have proved that sea slugs are capable of containing chemicals from the creatures they ate hours before.

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Sea Slugs are well-known for the many canine deaths that they cause. Remember that it is really important not to touch any brilliant and colored thing you see under the sea because sometimes the colorful creatures are the most dangerous of all. That’s why it’s very important to go scuba diving with an instructor since they’re always familiar with the indigenous marine fauna.

#7. Fire Coral

The Fire Coral is not actually a colonial marine. In fact, they are members of the Hydrozoa class which is similar to a jellyfish. Most of them are located in the Indian, Pacific and Caribbean Ocean. Like many coral reefs, these creatures are suffering from pollution and the damage that human actions are inflicting upon the sea.

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Maybe they are not the friendliest creatures that you can find under the sea, but nothing will happen to you if you don’t get too close to them. If you touch any of them by accident, the contact may cause you burning and a raised rash. Keep on reading to see the last 6 most dangerous sea creatures that live under the sea!

#6. Beaked Sea Snake

According to research carried out within the Thai National Park, the bite of a Beaked Sea Snake contains one of the most powerful venoms in the world, causing the majority of envenomings and fatalities in the area. Located along the coasts of the Indian and Pacific Ocean, it’s better to stay away if you ever see one of them!

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In general, the Beaked Sea Snake is active during the day and at night and they can stay for more than five hours underwater before resurfacing. They’re considered to be the most savage sea snake in the world and their main source of food is fish, so at least we are safe from one thing! See the last 5 most dangerous sea creatures!

#5. Stargazer

Stargazers have special skin that makes it difficult to spot them when you’re diving. On top of this, most of them like to hide under the sand so it’s common for people to step on of them by accident. Stargazers are really poisonous because they have two large venomous spines that may cause you bleeding, pain, and electric shocks.

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In some cultures, Stargazers are a delight because the venom is not poisonous after the fish is cooked, and in fact, it’s very common to find these fish in many coastal markets around the world. Of course, chefs have to remove the electric organ Stargazers have. Thanks to the way in which they capture their prey, Stargazers are considered “the meanest things in creation”.

#4. Crown-Of-Thorns Starfish

The Crown-of-thorns Starfish is literally the Queen of Starfish as it is one of the largest starfish in the world. Their name comes from their venomous thorn-like spines that cover their bodies. These spines may cause extreme pains that can last for almost 3 hours. Most of them are located in Australia, the area of the Red Sea, and the East African coast.

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These type of starfish are not aggressive and the only defense mechanism they have is their poisonous spines, and that’s why the spines can cause big injuries to the skin of an animal or a person. Some of them are found on coral reefs and rocks near the coast. Although they look really beautiful, remember to avoid them!

#3. Portuguese Man-Of-War

The Portuguese Man-of-War is a marine Hydrozoan located in the Atlantic, Indian and Pacific Oceans. Even though they look innocent, their long tentacles (more than 165 of them!) are covered by a strong venom that can paralyze their prey. Luckily, it’s not mortal to humans but it can cause a lot of pain and in some extreme cases it can even provoke paralysis.

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Every summer in Australia, the man-of-war is responsible for more than 10.000 humans stings. Some of them appear at the coast of the beaches and people maybe don’t realize that the tentacles are still drifting and contain powerful venom. The most common injury that Portuguese man-of-war cause to humans is the red welts on the skin, that can last for almost three days.


Maybe nothing that we have read can be compared to the terrible and terrifying attack of a Candiru. They are located in South America, in countries like Bolivia, Brazil, Colombia, Ecuador, and Peru. The largest Candirus are no longer than 40 centimeters, but as we’ve said before, sometimes the smaller creatures are the most abominable predators that you can ever find under the sea. 

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Candirus are known for feeding on blood and the smaller ones are known for invading and parasitizing the human urethra. The Candiru’s bite can cause hemorrhage and on rare occasions, death. But the scariest thing about these fish is that their body is translucent so it’s hard to see them under turbid waters. Can you guess which is the most dangerous sea creature that exists on Earth?

#1. Striped Surgeonfish

We know that at first sight, the Striped Surgeonfish can look adorable and even perfect as a pet. But don’t let their appearance fool you, because one of their bites can cause you deep wounds in your skin. They’re no longer than 40 centimeters and most of them are well-known because of their black-edged blue and yellow stripes.

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Located in the Indian and Pacific Ocean, they live in reefs and just a few meters beneath the ocean’s surface. The other defensive mechanism they have is their caudal spines which contain venom. Remember that many creatures that live under the sea can be really beautiful at first sight, but it’s always advisable to keep a distance and to be very cautious when diving because you never know how dangerous they may be.

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