Sharks Are Not the Most Dangerous Ocean Animal

Encounters with these animals can prove painful. Or deadly.

Most Dangerous Ocean Animals

The ocean is a wondrous place. It also can be extremely dangerous. Currents and pressure are part of the danger, but many animals that lurk within the water can be another risk.

Some underwater species, like sharks, are well-known and feared. But several lesser-known species can prove deadly, and swimmers, snorkelers or divers should be aware of them, too.

These are the most dangerous ocean animals.

15. Lionfish

Humans killed: 0

Habitat: Indo-Pacific region, Caribbean, Gulf of Mexico

Notable features: Colorful, stripped spikes that protrude from its body.

Note: Some of the animals on this list are dangerous for attacking humans, not necessarily killing them.

What Makes Lionfish So Dangerous

There are no recorded fatalities linked to lionfish, but the spines that create a "mane" around them are full of venom. If you touch a lionfish without knowing how to handle it, you will be subjected to excruciating pain.

Where this becomes dangerous is if this happens as you’re in the water. The pain could be so bad you might not be able to swim back to the surface.

If you see one of these in the water, stay away.

14. Moray Eel

Humans killed: 0

Habitat: Warm waters of the Atlantic, Pacific and Indian Oceans

Notable features: Long bodies without scales.

What Makes Moray Eels So Dangerous

Giant moray eel, underwater Gymnothorax miliaris

Like lionfish, moray eels have not caused a recorded death yet. Still, they can be aggressive when they perceive threats and can attack humans who swim too close to them.

Moray eels are also dangerous when ingested. Their toxic skin can cause serious illness when not cooked properly, so skip this delicacy unless you really trust the chef.

13. Flower Urchin

Humans killed: 1 (total ever recorded)

Habitat: Red Sea, west Pacific Ocean, Southeast Asia, South Pacific

Notable features: Pink and white valves that resemble flowers.

What Makes Flower Urchins So Dangerous

They may be beautiful to look at, but these are the most dangerous sea urchins, according to the Guinness Book of World Records. These creatures release venom when stepped on or touched.

The issue is not only the pain, but the possible paralysis that touching one may cause. Although only one death has been recorded, you can imagine how dangerous paralysis can be while in the water.

Most victims of sea urchins are snorkelers who step on them thinking they are corals. One more reason to keep your hands and feet off reefs.

12. Leopard Seal

Humans killed: 1 (total ever recorded)

Habitat: Antarctica

Notable features: Gray fur with black spots.

What Makes Leopard Seals So Dangerous

Although only one person has been known to be killed by a leopard seal, there have been several other recorded attacks.

Leopard seals are known to be aggressive predators, and most of the people who have been bitten or dragged into the water by them have been scientists.

The low number of incidents may be due to the fact that most people don’t ever make it to Antarctica, so the species’ interactions with humans are very limited.

11. Stonefish

Humans killed: 2-3 (total ever recorded)

Habitat: Coastal waters of Australia, Indonesia and India as well as a few species in the Caribbean and Florida Keys

Notable features: Camouflage as a rock or reef.

What Makes Stonefish So Dangerous

Like flower urchins, stonefish deploy venom when stepped on or grabbed. Since, as their name suggests, they look like rocks, many unsuspecting swimmers step on them and are then subjected to horrible pain. Paralysis and heart failure are also possible.

Stonefish have been named the most dangerous fish in the world due to their ability to kill a person within one hour of releasing venom. Global data for stings is incomplete, but in Australia, about 1,000 people step on a stonefish every year.

10. Blue-Ringed Octopus

Humans killed: 3 people (total ever recorded)

Habitat: Australia, Japan, Philippines, India

Notable features: Blue rings on its body.

What Makes Blue-Ringed Octopuses So Dangerous

In general, brightly colored ocean animals should not be touched, as it is often a signal of them being venomous. Blue-ringed octopuses are certainly attractive, but they have a venom that is more potent than cyanide by 1,200 times. This means one octopus could kill 20 humans.

The good news is that these octopuses are usually non-confrontational, so you are not likely to be attacked unless you provoke one.

9. Portuguese Man-of-War

Humans killed: 3 (total ever recorded)

Habitat: Tropical and Subtropical waters in the Atlantic and Indian Oceans

Notable features: Clear blue or purple bodies.

What Makes Portuguese Man-of-Wars So Dangerous

Also called "floating terror," this cool-looking animal uses its tentacles to sting prey as well as predators. Their sting is so powerful that, in a few cases, they have caused people to go into anaphylactic shock and die.

If you find one on the shore, be careful not to touch it. The animal can shock even after its death. Good samaritans picking up plastic bags at the beach should double-check to make sure they’re not confusing the animal with plastic waste.

8. Needlefish

Humans killed: 4 (total ever recorded)

Habitat: Warm waters around the world

Notable features: Long, thin bodies and sharp, pointy heads.

What Makes Needlefish So Dangerous

All of the deaths caused by needlefish have been freak accidents, but they’re gruesome enough to make us scared of the species.

Needlefishes have a tendency to jump out of the water to avoid obstacles rather than swim through them. Since they mostly live in shallow water, these obstacles are often boats. As the fish jump over the boats, they have sometimes stabbed people with their sharp, pointy heads.

People have bled to death due to the wounds or died when pierced in vital organs.

7. Sea Snake

Humans killed: 10 (total ever recorded)

Habitat: Indian Ocean, tropical waters of the Pacific Ocean

Notable features: Being able to survive underwater for long periods of time.

What Makes Sea Snakes So Dangerous

Snakes are some of the most dangerous animals on Earth, so it makes sense that sea snakes would be on this list. Sea snakes are part of the cobra family and are usually venomous. They can kill eight people with just three drops. Scary.

Though less than a dozen people are reported to have died due to sea snakes, as many as 75,000 fisherpeople are bitten every year. Deaths are more likely to happen in remote regions where antivenom is not widely available, so the numbers could be much higher.

6. Stingray

Humans killed: 17 (total ever recorded)

Habitat: Warm waters around the world

Notable features: A venomous stinger at the end of its tail.

What Makes Stingrays So Dangerous

In general, stingrays are gentle creatures that only attack when they feel threatened. Fatalities have usually been caused when the sting pierces a vital organ or causes heart failure, as was the case with Steve Irwin, known as the Crocodile Hunter.

While deaths are not common, there still are about 1,500 yearly stingray attacks in the U.S. alone. Stings may cause cramps, swelling and a heck of a lot of pain.

5. Cone Snails

Humans killed: 36 (total ever recorded)

Habitat: Tropical, warm waters

Notable features: A cone-shaped shell with blotchy orange coloring.

What Makes Cone Snails So Dangerous

You wouldn’t think a snail could kill a human, but cone snails are so venomous they can kill 20 people with a single drop.

They are usually found in reefs, and most incidents have happened due to people trying to collect a pretty seashell.

Our advice is simple: Do not touch anything when you’re snorkeling or diving unless you’re an expert.

4. Pufferfish

Humans killed: 6-7 per year

Habitat: Warm waters of the Indian, Pacific and the Atlantic Oceans

Notable features: A spiked body that inflates when agitated.

What Makes Pufferfish So Dangerous

Pufferfish blow up when irritated or threatened, as "Finding Nemo" taught us. This is a way to let potential threats know to back off. Given the fish’s notoriety, most people know not to touch it because it is extremely venomous.

However, that doesn’t keep humans from trying to eat it, despite it being poisonous when consumed. In Japan, pufferfish is a delicacy. When cooked right, it poses no threat, but if the chef doesn’t know what they’re doing, eating it can cause paralysis or death.

3. Shark

Humans Killed: 10 per year

Habitat: Every ocean on the planet

Notable Features: Sharp teeth and a tall dorsal fin.

What Makes Sharks So Dangerous

To be fair, the vast majority of shark species rarely even interact with humans. Those that do, rarely attack. In fact, humans pose a greater threat to sharks than sharks do to us.

Still, sharks do attack humans. In 2020, there were 57 shark attacks around the world. Each year, about ten of these attacks are fatal. Even when attacks don’t result in death, they can leave victims with permanent health issues or loss of limbs.

There are also certain species of sharks that are known to be aggressive and attack humans when unprovoked, namely great white sharks and bull sharks. The latter has a habit of going into rivers, which is truly horrifying.

2. Saltwater Crocodile

Humans killed: 10-15 per year

Habitat: Indo-Pacific region

Notable features: The most powerful jaw in the world.

What Makes Saltwater Crocodiles So Dangerous

Saltwater crocodiles have the most powerful bite in the world. They can break a skull with a single bite. To make matters worse, they are much more aggressive than other similar species like alligators and are known to attack and even hunt humans. And while most crocodiles are in rivers, they can use currents to go deep into the ocean.

Each year, this species attacks 20 to 30 people. Around half of the attacks prove fatal. The good news is that education and warning signage has helped lower fatalities. Still, if you’re somewhere with saltwater crocodiles, keep your wits about you.

1. Box Jellyfish

Humans killed: 50-100 per year

Habitat: Indo-Pacific, Australia

Notable features: Long tentacles.

What Makes Box Jellyfish So Dangerous

We all know a jellyfish sting is unbearably painful, but few of us think it can actually lead to death. As the most venomous marine animal, the box jellyfish is responsible for up to a hundred human deaths per year. This high fatality rate is caused by their quick-acting venom, which can kill someone in five minutes.

What is also scary about box jellyfish is that they are the only species of jellyfish that can move at will rather than float around waiting for things to get caught in their tentacles.