Venomous Marine Creatures: Ones You Will Want to Avoid
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When we think of venomous animals, we typically imagine snakes, spiders, and other terrestrial creatures. But lurking in the depths of the ocean, there are lots of venomous marine animals.
Do keep in mind that being venomous and being poisonous are two different things, and in this guide, we’ll be looking at the former.
Typically, venomous sea creatures will use their venom as a form of defense against predators. But I’m sure you’ll also want to avoid getting on the wrong side of them!
Venomous Fish & Sea Snakes
There are more than 1200 species of venomous fish in the world and that’s a scary thought. Some won’t do a lot of harm to humans, while a bite or sting from another could be fatal. Here’s a list of some of the potential threats that are lurking beneath the waves.
Reef Stonefish (Synanceia verrucosa)
Venom Delivery Method: Spines
Stonefish are usually gray or brown but may have orange or yellow markings. The dorsal area is covered in spines, and while they are highly venomous, they are a popular aquarium pet.
Distribution & Habitat
The tropic of Capricorn in both the Pacific and Indian Oceans as well as the Red Sea. There is some evidence to suggest release of these animals in the Mediterranean Sea and the Suez Canal. They typically live around coral reefs and rocky areas but can also be found on the ocean floor.
Toxicity
The stonefish is the most venomous fish in the world and delivers its toxins via 13 spines. The sharp spines have the potential to pierce thick-soled boots, and as little as 18 mg can prove fatal to humans. Other symptoms may include tissue death and paralysis; however, death usually only occurs in vulnerable people such as the elderly, children, and those with immune system problems.
Red Lionfish (Pterois volitans)
Venom Delivery Method: Spines
Red lionfish are indeed one of the most beautiful venomous fish with reddish brown bands and ornate spines. Despite being toxic, they’re a very popular marine pet that can grow up to 15 inches (38 cm) in length.
Distribution & Habitat
The red lionfish is a type of coral reef fish that is found in tropical waters, particularly in Indo-Pacific regions. They’re commonly found in Malaysia and South Korea, all the way North to Japan. However, it has been introduced to the Caribbean Sea, where it’s deemed an invasive species.
Toxicity
Lionfish use their spines to deliver venom as a method of protection. While humans may be stung, it’s rarely fatal. You may suffer from unpleasant symptoms such as headaches, difficulty breathing, and vomiting, but at-home treatment is usually all that’s necessary.
Scorpion Fish (Scorpaenopsis spp.)
Venom Delivery Method: Spines
There are several types of scorpionfish within the family scorpaenidae, including the false stonefish (scorpaenopsis diabolus), which is often mistaken for the stonefish. Much like their relative, the lionfish, scorpionfish have spines, most of which are located along the dorsal fin with some on the anal fin.
Distribution & Habitat
While there are examples of scorpionfish in the Atlantic Ocean, they’re typically native to the Indo-Pacific region. They prefer brackish waters as well as marine environments. While they prefer surface water, some are known to go as deep as 2600 ft (790 meters).
Toxicity
For sea animals, a sting from a scorpionfish can be fatal. But for humans, the worst result is usually extreme pain.
Much like the lionfish sting, at home treatment including warm compresses and removing any leftover spines with tweezers is the best method.
Weever Fish (Trachinidae)
Venom Delivery Method: Spines
The weever fish might look cute and harmless but it certainly packs a punch.
Distribution & Habitat
These fish are often found in shallow water, hiding out in the sand on the seabed. They’re common in the Mediterranean Sea but have been reported along the southern coasts of the UK.
Toxicity
Most humans are stung when they accidentally step on a weever fish. In most cases, symptoms are mild and may include localized pain, nausea, headaches, and itching but will typically subside by themselves.
In some rare cases, more severe symptoms may arise, including breathing difficulties, seizures, and abnormal heart rate. Hospital treatment may be required in these cases, but there has only ever been one reported death, and that was in 1933.
Stargazer (Uranoscopidae)
Venom Delivery Method: Spines
If the poor stargazer fish didn’t have a reputation for being venomous, it would still be plagued by its rep as one of the ugliest fish in the world. The eyes are located on the top of the head, which is where the fish gets its name, and the upturned mouth and boxy features almost make it look like a bulldog.
Distribution & Habitat
These fish are found all over the world and inhibit shallow marine waters. However, they’re most common in Mediterranean and Atlantic waters.
Toxicity
Not only is the stargazer venomous, but its eye spines can also deliver an electric shock. When stung, you may feel pain, and the area will become red and swollen. In some cases, victims may experience symptoms of shock but you’ll be unlikely to die. These fish are known to be particularly aggressive, so should be avoided.
Short-Tail Stingray (Dasyatis brevicaudata)
Venom Delivery Method: Stings
Generally speaking, the stingray is a docile animal that poses a very low risk to humans. These are bottom-dwelling fish that can grow to over 7 foot (2 meters). Short-tail stingrays are the largest of all stingray species.
Distribution & Habitat
Short-tail stingrays can be found off the coast of Southern Africa as well as all around Australia and New Zealand. While they are more commonly found in shallow waters and around coral reefs, they will sometimes venture a little further out.
Toxicity
The short-tail stingray earned itself a bad reputation when naturalist, Steve Irwin, was tragically killed by one. While the event was caught on camera, it was never released to the public, and fortunately, fatalities from these creatures are incredibly rare.
Steve was killed because the stingray’s barb pierced his chest. All other fatalities with stingrays are caused this way. The stingray has one venomous barb on its spine.
Yellow Boxfish (Ostracion cubicus)
Venom Delivery Method: Skin contact
The yellow boxfish looks adorable but it’s a lot more deadly than its appearance might let on. Sometimes called the cowfish, these seemingly sweet little animals are often caught as marine pets.
They are small fish which don’t tend to grow much bigger than 18 inches (0.5 meters) maximum. While boxfish do come in different colors, and there are up to 24 species, the yellow boxfish is perhaps the most well-known.
Distribution & Habitat
The yellow boxfish can be found among rocky reefs. They’re very common off the east coast of Australia but can be found throughout the Indian and Pacific Oceans as well as in some southeastern parts of the Atlantic.
Toxicity
When the yellow boxfish feels threatened or distressed, it will release a tetrodotoxin from its skin. Simply coming into contact with the toxin probably won’t do you much harm but since boxfish can be eaten, improper preparation can lead to poisoning and fatalities have been reported.
You really wouldn’t want to eat one when it wasn’t cooked, as the toxins can cause your red blood cells to rupture!
Striped Surgeonfish (Acanthurus lineatus)
Venom Delivery Method: Spine
Striped surgeonfish is a popular marine pet thanks to their beautiful patterns and colors as well as their pancake-like appearance. They can grow to around 15 inches (38 cm).
The fish is now protected as it has been sadly exploited in parts of the world due to its value to aquarium owners.
Distribution & Habitat
These fish prefer shallower waters and are commonly found around coral reefs. They’re very widespread going all the way from Africa, through the Indian Ocean, down to Australia, through Asia, and as far out as Hawaii.
Toxicity
The striped surgeonfish has a single toxic spine called the caudal spine. This spine is used for predation and protection and isn’t usually harmful to humans. However, if you handle the fish incorrectly then you may be stung.
The spine is surgically sharp which is where the fish gets its name and can cause a nasty skin injury if it catches you.
Dubois’ Sea Snake (Aipysurus duboisii)
Venom Delivery Method: Bites
The Dubois sea snake is one of the most venomous sea snakes and it is also among the top three most venomous snakes on both sea and land!
Distribution & Habitat
Found in coastal waters around all but the south coasts of Australia as well as along the shores of Papua New Guinea, New Caledonia, and other South Pacific islands. While they prefer shallow water, they can dive up to 260 feet (80 meters).
Toxicity
Dubois sea snakes have a neurotoxic venom which has the potential to cause death in humans, although this is incredibly rare. Paralysis is not uncommon after a bite due to muscle breakdown.
However, since the snake only has very small fangs and is unaggressive, it’s rare for humans to be attacked. Moreover, antivenins are widely available.
Yellow-Bellied Sea Snake (Hydrophis platurus)
Venom Delivery Method: Bites
With deep black coloration and a bright yellow underbelly, this is certainly a sea snake that catches your attention. However, there have been ample warnings to divers to watch out during the yellow-bellied sea snake’s mating season as these animals are known to become aggressive and even mistake humans for a potential mate.
Distribution & Habitat
Yellow-bellied sea snakes are found in tropical oceans all around the world. The only ocean they are absent from is the Atlantic. They can be found near the surface where they use the current to get around.
Toxicity
The venom of these snakes contains iso toxins and neurotoxins, and they’re known to be one of the deadliest snakes. While there are no recorded yellow-bellied sea snake deaths to humans, the bite can cause muscle pain and total paralysis. There are antivenins available and it’s also possible to treat a bite with tiger snake antivenom.
Belcher’s Sea Snake (Hydrophis belcheri)
Venom Delivery Method: Bites
Similar to the yellow-bellied sea snake, there’s a potential for the Belcher’s sea snake to attack during mating season. However, usually, these are quite placid snakes and would sooner swim away than confront a human.
Sometimes called the faint-banded snake, these animals have lightly colored bands around their body and will grow up to around 3 feet (1 meter) in length.
Distribution & Habitat
They are found in the Indian Ocean and around the coasts of Australia. They are commonly found in reefs and many have been noted in places like the Ashmore Reef.
Toxicity
The Belcher’s sea snake possesses venom that contains neurotoxins which will cause numbness, paralysis, and eventually death. When first bitten, you won’t feel pain, so may not even realize it until it’s too late.
The good news is that bites to humans are very rare.
Venomous Mollusks
The most venomous animal in the world is a mollusk, the cone snail. But this isn’t the only type of invertebrate that you need to be worried about when stepping into the ocean.
Cone Shells (Conus spp.)
Venom Delivery Method: Stings
The cone snail is known to be the most venomous animal in the world and can kill a human in just a few minutes.
One identifying feature is the way they hunt. When they sense prey, the snail releases its proboscis and uses a sharp tooth to inject venom.
Distribution & Habitat
Most notably found in Indo-Pacific waters, but cone snails frequent warm, tropical waters all over the world as well.
Toxicity
These creatures have incredibly potent venom, and just one snail has enough to take down as many as 20 people. However, there are around 800 different species of cone snail, each with varying levels of danger.
Smaller species with less potent venom may only produce symptoms akin to a bee sting. However, the more dangerous cone snails can cause respiratory failure, muscle spasms, and paralysis. Currently, there is no antidote if you are stung.
Blue-Ringed Octopus (Hapalochlaena spp.)
Venom Delivery Method: Bites
The blue-ringed octopus is a small species and incredibly beautiful, with bright markings of blue and green. The signature black rings only appear when the animal feels threatened.
Distribution & Habitat
Often found in tide pools, blue-ringed octopuses are found in the Pacific and Indian Oceans. They can also be found living around coral reefs.
Toxicity
Blue-ringed octopuses have a toxin called tetrodotoxin which is 1000 times more powerful than cyanide! Despite how dangerous it is, there have only been three recorded deaths from a bite.
But if you are unfortunate enough to be bitten, there’s currently no antidote. Heart massage and respiratory assistance are the only known treatments.
If you evade death, you may experience symptoms such as sensory and motor skill loss, nausea, paralysis, loss of vision, and respiratory failure. Each octopus has enough venom to kill up to 20 people in a matter of minutes!
Nudibranch (Nudibranchia)
Venom Delivery Method: Spines
One of the most fascinating things about the nudibranch, a type of gastropod, is its beautiful coloration. They come in striking colors like blues, greens, and yellows and there are as many as 3000 known species!
Distribution & Habitat
Depending on the species, the nudibranch can be found all over the world. Often called sea slugs, they’re found in cold waters like the Antarctic, as well as warm, tropical waters. Most species inhabit saline waters, although there are a few examples that can be found in brackish environments.
Toxicity
Not all species of nudibranch are venomous, but some have spines that contain venom along their sides which are largely used as protection. Most species, aside from one; the blue glaucus (glaucus atlanticus), will stay away from humans.
If you are stung by a sea slug, then the neurotoxins could cause paralysis and breathing difficulties. However, the venom will not affect the heart or the brain. In most cases, you will experience moderate pain, but the likelihood of death is incredibly rare.
Venomous Jellyfish, Sea Urchins & Starfish
Jellyfish are among some of the most feared creatures in the ocean, and for good reason. Just brushing against their tentacles can cause a fatal sting. However, there are also a variety of sea urchins and starfish that can have similar effects.
Box Jellyfish (Chironex fleckeri)
Venom Delivery Method: Stings
Sometimes called the sea wasp, box jellyfish have tentacles that can grow up to 10 feet (three meters). Each jellyfish has as many as 15 tentacles attached to its relatively small body. While dangerous, they are incredibly beautiful.
Distribution & Habitat
Indo-Pacific waters including waters along Northern Australia and the Philippines. Box jellies prefer to swim in coastal waters.
Toxicity
The box jellyfish sting can be fatal. It delivers its neurotoxic venom though cells called cnidocytes, which when touched, are activated. Symptoms can include cardiac arrest, pain, difficulty breathing and paralysis.
The toxins act quickly, with symptoms showing mere moments after being stung. However, there is an available antivenom which can be given intravenously and can be used to prevent death.
Portuguese Man o’ War (Physalia physalis)
Venom Delivery Method: Stings
Many people refer to the man o’ war as a jellyfish but while it’s similar, it’s actually a siphonophore; basically a different species that’s made up of several smaller gelatinous creatures.
Even more odd is that these creatures cannot move themselves but rather rely on the current to carry them.
Their tentacles can get as long as 165 feet (50 meters), and it’s even possible for them to detach and remain just as dangerous. So, if you see one, stay away!
Distribution & Habitat
Found throughout the world, usually in groups of up to 1000 or more. They prefer warmer waters.
Toxicity
The man o’ war is unlikely to kill a human as its venom isn’t strong enough. However, it can cause pain and severe skin irritation. However, there are some people that have an allergic reaction to the venom of siphonophores and this can result in difficulty breathing, which can be dangerous when in the water as the person can end up drowning.
The toxins are designed to kill prey and these ‘jellies’ are able to kill surprisingly large fish with just one sting.
Lion’s Mane Jellyfish (Cyanea capillata)
Venom Delivery Method: Stings
The lion’s mane jellyfish is the largest species of jellyfish in our oceans and one of the most interesting to look at, with tentacles that look just like a lion’s mane!
The largest ever recorded example of this jellyfish was found in the 1800s and measures 83 inches (210 cm) across! Its tentacles stretched a whopping 120 feet (37 meters)!
Distribution & Habitat
Cold waters including the Arctic and Atlantic Oceans. Mainly found in deeper waters, so it doesn’t often come into contact with humans.
Toxicity
Lion’s mane jellyfish are not terribly toxic to humans. In most cases, the sting will result in redness, mild pain, and swelling to the local area. However, this will typically clear up without treatment. The only time that you would require medical treatment is if you have an allergy to the jellyfish’s toxins.
Flower Urchin (Toxopneustes pileolus)
Venom Delivery Method: Spines
These fascinating creatures are sometimes called trumpet urchins and can grow up to 8 inches (20 cm). They have a stunning appearance, but looks can be deceiving as these are known to be the most dangerous type of sea urchin.
They deliver their venom through cup-like structures that close when disturbed, releasing their toxins. The adults are made up of several segments that sit around a central axis.
Distribution & Habitat
Mainly found in Indo-Pacific waters on the sea bed and around coral reefs or rocks. They also tend to live in seagrass beds to a depth of around 295 feet (90 meters).
Toxicity
Flower urchin stings can be incredibly painful and there are cases where people have been reported to have drowned being unable to swim to shore with the pain.
When stung, you may also suffer from nausea, high blood pressure, tingling, and difficulty breathing. The sting is unlikely to be fatal, and treatment involves topical creams, warm compresses, and pain relief.
Fire Urchin (Asthenosoma spp.)
Venom Delivery Method: Spines
The fire urchin actually belongs to the same family of creatures as the starfish. It can grow up to ten inches (25 cm) across and is made up of plates that are loosely joined together. With its rich colors, the fire urchin literally looks like a glowing ember.
Distribution & Habitat
Widely found across the Indo-Pacific area as far North as Japan as well as South down to Australia. Fire urchins prefer rubbly or sandy seabeds
Toxicity
The fire urchin’s toxins are rarely dangerous to humans. If you are stung, it’ll be painful but usually, there won’t be any other symptoms unless you have an allergic reaction to the toxin.
Irukandji Jellyfish (Carukia barnesi)
Venom Delivery Method: Stings
The Irukandji jellyfish is a relative of the box jelly and is just as feared owing to the fact that its toxins are incredibly potent. However, this is also the smallest jellyfish in the world so can be mistaken for something harmless. A fully grown adult may not be any larger than 1cm³.
Distribution & Habitat
North and East coasts of Australia, particularly around Queensland. Although they are said to be spreading as far as Florida and the United Kingdom.
Toxicity
When stung by the Irukandji jellyfish, you will suffer from Irukandji syndrome, which involves symptoms such as muscle pain, headaches, nausea and vomiting, abnormal heart rate, difficulty breathing, and many others. These symptoms can take as long as 2 weeks to clear, but fortunately, since treatment for stings is available the threat of death is minimal.
Crown-of-Thorns Starfish (Acanthaster Planci)
Venom Delivery Method: Spines
The crown of thorns starfish is perhaps most well-known for the effect it is having on coral reefs. It feeds on coral, eating through reefs far more quickly than the reef can reproduce. For this reason, humans are currently trying to control the population.
These thorny animals have up to 23 arms covering their bodies, and each of the arms is covered in venomous spikes. Divers are being warned not to touch them unless they want to receive a nasty sting.
Distribution & Habitat
The crown of thorns starfish inhabit coral reefs and can be found throughout the Indo-Pacific region.
Toxicity
Crown of thorn starfish have toxins that contain saponins. When injected into a human via the spines, these can cause severe pain, redness, and swelling. These symptoms will typically last a few hours, although there are reports of recovery taking several weeks.
Should you be unlucky enough to end up with a spine lodged in your skin, the only solution is to have it removed during surgery.
What is the Difference between a Poisonous and Venomous Marine Creature?
The terms poisonous and venomous are often used interchangeably. However, there is a difference. Both poisonous and venomous creatures can cause damage but how they deliver this damage is where things are different.
For example, a sea creature that is venomous will deliver its toxins via a bite or a string. This includes animals such as the stonefish or certain species of jellies. On the other hand, a poisonous animal cannot sting or bite you, but if you eat it, then toxins are released that can make you sick or even kill you.
But that doesn’t mean that you can’t eat poisonous sea creatures. It means that you have to be mindful of how you prepare them; at least in the case of the fugu pufferfish, which is considered a delicacy in Japan. They love it so much that more than 10,000 tons are consumed in the country every year. But cook it wrong, and the toxin tetrodotoxin could produce more deadly symptoms than cyanide!
There is such potential danger surrounding fugu that not just anyone can cook it. Chefs must undergo special training and receive certification before they’re allowed to serve fugu to the public. This is one of the reasons that the fish is so expensive; $200 per plate, to be exact. Improper preparation sees around 20 people a year killed from eating this delicacy.
Medicinal Uses of Venom from Marine Creatures
Many of us may live in fear of sea creature venom when we enter the ocean. But it’s not all bad. In fact, scientists have discovered ways that venom from some of the most seemingly dangerous sea animals could have medicinal properties.
One of the most notable recent discoveries is that the venom from the cone snail contains a type of chemical called conotoxins that may be the key to improved pain medication. As far as research shows us, these conotoxins could be used to make new analgesic medication that’s far more effective than morphine.
There’s obviously a long way to go with this and further development is required. One of the main concerns is improving the biodiversity of the species in order to further discover the potential of their venom.
And where pain relief is concerned, a type of sea anemone found off the coast of Australia, could be the answer to chronic back pain, according to researchers. These creatures have venom that contains as many as 84 individual toxins but one of these is something we haven’t seen before, and this could be the key to new medication.
If scientists can isolate the toxin, there is potential that they could use it as a neurological blocker in the treatment of conditions such as back pain.
If that wasn’t enough, scientists are currently looking at the possibility of developing a new, cleaner way of delivering drugs through the use of sea anemone stinging cells. There’s still a lot of research to be done on this, but it’s paving the way for the future of medicine.
There is also a suggestion that eventually, we will be able to use the venom of certain sea snakes to cure everything from liver disease to brain issues. This is because of how the snakes have adapted certain chemicals in their bodies through evolution to become toxins.
How to Stay Safe from Venomous Aquatic Creatures When Diving or Swimming
Getting into the water is always a pleasure, but we have to remember that we are entering the habitat of these sea creatures. If they feel threatened, they may attack. Moreover, some of them can’t even help it, and merely rubbing against them will cause a sting.
That doesn’t mean you can’t enjoy the ocean, you just need to be respectful of it and take the right precautions.
1. Ensure Your Body is Fully Covered
The less skin you expose when in the water, the less chance there is of getting stung. This is why wearing a full body covering such as a wet suit is incredibly important, especially in waters where there are lots of stingers. During stinger season, you should avoid going into the water at all.
2. Wear Diving Gloves & Boots
It can often be difficult to see what’s on the ocean floor especially in deep or murky water. This is why you should always wear diving boots or even simple water shoes to prevent you from being stung by anything you may stand on. Any shoes you wear should have a thick enough sole that stingers cannot penetrate.
It’s also essential to protect your hands as these are often the one thing that are left exposed. Diving gloves allow you to stay safe while not affecting your dexterity. You’ll also have the added benefit of protection from cuts on things like rocks or coral which can be very sharp.
3. Avoid Touching Any Marine Creatures
In most cases, venomous sea creatures won’t attack unless they feel threatened. Remember that you are in their home; you wouldn’t want someone coming into your home and touching you, so offer them the same respect.
Of course, we want to take in their beauty, so spend some time observing them but remember the golden rule: look, don’t touch!
When moving around in the water, pay close attention to what is ahead of you. Jellyfish can be easily missed, so you should make sure to look all around you, including above and below you, before proceeding. Merely brushing against a jelly can result in a fatality.
4. Be Careful Where You Place Your Hands & Feet
One of the most common ways that people are stung or bitten by venomous sea creatures is when they touch or stand on them accidentally. The problem is that a lot of these animals will blend into their surroundings. For example, the stonefish camouflages itself on the ocean floor.
Even when you are wearing gloves and appropriate water shoes, it’s still worth looking at where you place your hands and feet before actually setting them down.
5. Practice Good Buoyancy Control
If you’re learning to dive, buoyancy control is one of the most important things to master. This will keep you off the bottom, which reduces the risk of making contact with a venomous creature.
6. Shuffle Instead of Walking When Getting into the Sea
Most animals will make a dash for it rather than having to face a potential predator and protect itself. This means that if you make a scene when moving through the water, you’re likely to scare them away before you make contact with them.
Instead of walking through the water, use a shuffling motion. This is particularly good for getting animals buried in the sand to move and stops you from treading on them.
