Top 10 Deadliest Marine Animals

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It’s hard to imagine that the surface area of the earth is made up of 70% water, and that as advanced as we humans are, we haven’t even come close to exploring all the water available to us. Although scientists have made rough calculations telling us that over 1200 dangerous sea animals exist and are the result of at least 50 000 people getting hurt each year, it could very well be that there are another 1200 dangerous sea animals that we don’t even know about yet! Nonetheless, taking into account the deadly marine life that we do know about, here is a list of ten of the most dangerous marine creatures known to man. Scuba divers, snorkelers, swimmers and free divers take note!

The Textile Cone Snail

Although exquisite to look at, the Textile Cone Snail is one of the most toxic marine creatures in the whole world. Just a solitary drop of their deadly venom can kill up to 20 full-grown men! The saying that dynamite comes in small packages is certainly true in this case as the Textile Cone Snail is a very small creature with tiny harpoons that deliver the deadly neurotoxin. These harpoons, which are essentially teeth that have been modified over time, are able to penetrate not only skin but diving gloves and wetsuits too. Affecting specific nerves of its victim’s body, the toxin is able to rapidly paralyse the victim’s respiratory system, causing death soon after. The scary fact of the matter is, the Textile Cone Snail’s neurotoxin does not have the same effect on every victim – some victims will feel nothing but a small amount of pain from where the harpoon broke the skin. In these cases, the victim will have a few days without any life-threatening symptoms but once the neurotoxin kicks in, the victim is highly likely to die. Luckily for us scuba divers, Textile Cone Snail stings are rare. These tiny but deadly creatures have been the cause for only a few deaths over the long history of scuba diving.

Blue Ringed Octopus

The Blue Ringed Octopus is further proof that dynamite comes in small packages. This beautiful master of camouflage can usually be found hiding in small nooks and crannies around the sea floor and coral reef systems, specifically in the warm Indian and Pacific oceans. Although it may appear similar to an average octopus, this small creature certainly packs a punch and not unlike the Hulk, you wouldn’t like them when they’re angry. When threatened, the Blue Ringed Octopus emits a warning sign in the form of its bright, near-pulsating rings. If you experience so much as a small scratch from this octopus you could be in grave danger. One of its toxins, known as tetrodotoxin or TTX, is unbelievably 1200 times more powerful than cyanide. The neurotoxin begins by paralysing the victim’s body, leaving them entirely alert but unable to move. After total body paralysis, the victim’s lungs will stop functioning and, if treatment is not given, death will occur soon after. There is unfortunately no anti-venom for this deadly neurotoxin and the victim will usually be placed on life support until the effects of the tetrodotoxin cease to impact the body so severely.

Flower Urchin

Urchins are sharp, spiky creatures that can be rather unpleasant to stand on or lay an ill-placed hand on. Although these types of urchins are relatively common and most divers know to avoid getting too close to them, there’s one type of urchin that packs an even bigger punch. The Flower Urchin holds the Guinness Book of Records title for being the most dangerous urchin in the world. The Flower Urchin contains powerful venom that can be deadly in large quantities. The venom contains two toxins which can cause a series of unappealing reactions. The toxic protein known as Peditoxin causes anaphylactic symptoms which could cause inability to breathe or death. The second toxin is a neurotoxin known as Contractin A which causes major spasms in your body’s smooth muscle. The Flower Urchin, although it appears innocent, will deliver this venom to its unsuspecting victims through its pedicellariae, or flower-like spikes. To make matters worse, the pedicellariae may break off whilst still attached to the victim’s skin, meaning that it is still possible for this deadly creature to continue pumping toxins into its victim long after the pedicellariae detaches from the main urchin body. As a word of caution, the larger the pedicellariae, the more violent the venom is.

Sea Snake

Most commonly found in the Indian and Pacific Oceans, some sea snake species are extremely venomous and dangerous, some even more so than land snakes. According to scientists, sea snakes have evolved quite significantly from land snakes, and now have a very large lung that takes up almost the entire length of the snake, allowing them to thrive in their new underwater environment. The venom from a sea snake is much more powerful than the venom from a land snake, as it would need to be considering their prey consists of small fish with the ability to quickly swim away from predators. Venom from the sea snake immobilizes these small fish so that the snakes can feast. Although their mouths and fangs are much smaller than land snakes, don’t disregard their ability to puncture the skin right through a wetsuit or gloves. Scuba divers are less likely to be bitten by sea snakes, however, as these creatures tend to be far more elusive and shy than their land counterparts. Sea snakes can also ‘dry bite’ without venom which is of course the best case scenario when underwater. Anti-venoms are available for sea snake bites and, although they are dangerous, sea snakes do not tend to claim many lives each year.

Stone Fish

The stone fish is considered the most venomous fish on earth and stings from this interesting-looking creature are unfortunately quite common. Although an anti-venom has been developed and has managed to save thousands of lives over the past century, it is imperative that a stone fish victim receives urgent medical attention. The neurotoxins located in the stone fish’s 13 sharp spines can cause paralysis of the respiratory system as well as failure of the heart. The stone fish is a master of camouflage and easily blends into the sea bed where unsuspecting divers or swimmers might step on them. Although the venom causes the sting to be extremely painful, victims are actually considered lucky if they get stung on the foot as opposed to other areas of the body, as it is then more difficult and time-consuming for the neurotoxins to reach the victim’s vital organs. Scarily enough, stone fish can also be found on land as they have been known to last up to 24 hours outside of the water.

Box Jellyfish

Can you imagine being in so much pain that you beg for your own limb to be cut off? This is what has happened with a number of box jellyfish victims when trying to deal with the unbearable pain caused from its multiple stings. With enough venom to destroy a total of 60 adults, these cube-shaped creatures have the deadliest sting known to man. The deadliest type of box jellyfish is known as the Sea Wasp and these are found in South East Asia and Northern Australia. They have been responsible for at least 60 deaths in recent years, and that’s just in Australia. All box jellyfish hold their venom in their long-stretching tentacles which continue to sting the victim even out of the water. The stings are cause for incredibly excruciating pain and cardiac arrest is expected within just 5 minutes of the first sting. Before death occurs, the pain is similar to being burnt with a hot iron, and unfortunately for the victim, the pain gets worse and worse before death occurs. An anti-venom has been developed, however, it is not as easily accessible as it should be.

The Barracuda

These torpedo-shaped predators can grow as long as 6 feet and are a force to be reckoned with both above and below the surface of the water. Although there are more than 22 barracuda species, luckily for us humans there is only one barracuda species that has been known to attack and even fatally injure humans, the Great Barracuda. These large game fish are armed with row upon intimidating row of razor sharp teeth which make them capable of inflicting serious harm when they’re on the hunt. Some barracuda species contain a very dangerous toxin, ciguateratoxin, on the surface of their skin. If humans come into contact with this toxin, the harmful symptoms can last for a number of months, causing serious discomfort and pain. Barracuda are unbelievably strong hunting fish and are attracted to small, shiny items that could be mistaken as fish. For us scuba divers, this can cause issues as much of our smaller scuba gear tends to be both small and shiny. Consider your dive knife or dive whistle – these items are prime examples of what could confuse barracuda and cause them to viciously attack under the assumption that they are getting a tasty meal. With their needle-like teeth and strong jaws, barracuda have been responsible for deep, brutal wounds that have caused humans to lose worrying amounts of blood and even experience nerve damage. Unfortunately barracuda do not only attack when underwater – they have been known to jump out and attack fishermen and other recreational boat users too. One of the most recent occurrences was in Florida in the United States. An unsuspecting canoeist was attacked by a barracuda and had to recover from broken ribs and a punctured lung that nearly cost her her life.

Leopard Seal

Leopard Seals may have lovely spotted coats that warrant closer inspection, but due to their aggressive nature (similar to their namesake) it is not at all recommended to get too close to them. Similar to leopards who live on land, Leopard Seals are unpredictable, quick to hunt and can be quite ferocious. With giant jaws full of razor sharp teeth, Leopard Seals are actually closer in appearance to reptiles and can weigh up to a massive 600 kilograms. Unsurprisingly considering their enormous size, Leopard Seals are one of the biggest seal species ever known to live in the southern oceans. The Leopard Seal’s large and extremely sharp teeth are used to feed on a host of different creatures such as fish, sea birds and penguins. Located at the top of the oceanic food chain in the Antarctic, Leopard Seals have even been known to kill humans so it is best to keep a safe distance if you come across one.

Saltwater Crocodile

Saltwater Crocodiles are phenomenal and deadly creatures that can grow to as long as 25 feet and have been recorded weighing as much as 2 tonnes. These incredible reptiles are dangerous when they’re on land and can move faster than you’d expect, but under water these creatures are to be avoided where ever possible as they can reach swimming speeds of 18 miles per hour. The Saltwater Crocodile has a bite that out-powers even the famous Great White – in fact, the croc’s bite is ten times more powerful which is a scary thought indeed. Saltwater Crocodiles are most commonly found in South East Asia, West India and Australia, however they are not limited to these locations. In fact, people have seen these intimidating reptiles as far afield as New Caledonia and Fiji. Saltwater Crocodile attacks in Australia are not hugely common, with only around 2 attacks per year for the past few years.


A top ten most dangerous marine animals list would not be complete without mentioning what most people would consider the most dangerous predator in the world – sharks. However, what many people don’t know is that with over 400 shark species roaming the waters, it is quite lucky that humans need only concern ourselves with a few aggressive species. Sharks have row upon row of razor sharp teeth and extremely large and powerful bodies that are certainly a force to be reckoned with in their natural habitats. Some of the largest sharks ever recorded weighed as much as 3 tonnes and measured as long as 25 feet. It’s amazing to consider that even at these enormous sizes, sharks can still move at speeds in excess of 35 miles per hour, giving us and their prey very little chance of escaping shark attacks if in the wrong place at the wrong time. The infamous Great White Shark is considered the most dangerous of all shark species, recording a total of 400 attacks globally. Only 20% of these recorded attacks have proved to be fatal, and usually these are as a result of mistaken identity – Great Whites tend to think that humans, especially humans on surfboards, look similar to sea turtles or seals which are some of their most hunted prey. With some of the other shark species, this does not always seem to be a case. Bull Sharks in particular, which are amazingly able to live in both saltwater and freshwater, have supposedly consciously attacked humans which is of course a major cause for concern. Bull Shark attacks tend to have a higher fatality rate than that of Great Whites, with 25% of Bull Shark attacks proving fatal. Tiger Sharks are another aggressive shark type that need to be given a wide berth and plenty of respect – like Bull Sharks, Tiger Sharks do not seem overly fussy with what type of animals they eat and females in particular can be very aggressive towards humans.

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