Who's up for a swim? Welcome to WatchMojo, and today we’re counting down our picks for the deadliest marine creatures that can– and have– caused immense harm to humans.
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00:00You're going to need a bigger boat.
00:02Welcome to WatchMojo,
00:03and today we're counting down our picks for the deadliest marine creatures that can and have caused immense harm to humans.
00:11These lethal tentacles can trail up to 15 feet.
00:15Number 30. Dolphins.
00:17Looks can be deceiving.
00:19Thanks to their features and reputations, dolphins are primarily seen as intelligent and even adorable.
00:25However, beneath that cute exterior lies a cold-hearted and often calculated mastermind.
00:31While most will interact calmly with humans, others will strike, especially if they feel threatened.
00:37This has caused some living in captivity to assault spectators, with a few fatal attacks happening in the 90s and in 2010.
00:44Kate, beware of sharks, sure, but beware of dolphins?
00:48Authorities are warning swimmers to watch out for Dusty the Dolphin, believed to be responsible for a number of attacks off the coast of Ireland.
00:56However, decades of the two species intermingling in a controlled environment has caused some people to be fearless around wild dolphins,
01:04despite the latter being unpredictable.
01:06Some people have ended up in the hospital, and there's little authorities can do. Dolphins are considered an endangered species.
01:14When attacks do occur, the injuries are often intense, with one case resulting in a damaged lung and spinal fractures.
01:21So, while they may look harmless and endearing, we recommend admiring them from afar.
01:27When the dolphin starts acting like a bucking bronco, I would move out of the way.
01:30Yes, when you realize it's about the size of a jet ski.
01:32Number 29. Giant Trevally.
01:35While this creature won't go out of its way to hunt humans, it does pose a significant threat to anyone who dares cross their path.
01:41Usually, they are solitary hunters, but about 50 of them have come here from neighboring reefs, attracted by this abundance of potential prey.
01:52Their means of attack is a repeated ramming of the head against their prey. Pretty brutal.
01:57While this is primarily used against other aquatic creatures, they have been known to charge towards people as well.
02:03If the Trevally are to catch one now, they have to up their game.
02:08One unlucky spearfisher suffered three broken ribs at the hands, er, well, head of a giant Trevally.
02:14These big guys will not hesitate to strike if they feel threatened, so you'd do well to stay out of their domain.
02:20Number 28. Fire Coral.
02:23When thinking of life forms that could cause injury, coral-like organisms probably don't even cross most people's minds.
02:29There's some nasty fire coral. It stings like a jellyfish.
02:34Despite their innocuous appearance, these small predatory animals, which aren't really coral, can have adverse medical effects.
02:41This hydrocoral has been documented causing extreme suffering in those who come in contact with it.
02:46The stings, caused by tiny tentacles similar to those found on jellyfish, cause immediate severe pain that can last up to weeks afterwards.
02:54Whenever somebody says, how will I know if I find fire coral? Oh, you'll know. Instantly. It's like touching a hot stove.
03:01There are also some nasty physical side effects to accompany the agony, including fevers and lesions.
03:07While there are several home remedies that can help relieve discomfort and reduce inflammation,
03:12some exposures are so intense that they require further assistance.
03:17Number 27. Blue Dragons.
03:20They may only grow to be a little over an inch long, but they can still cause a huge medical impact.
03:26These are small sea creatures. They look like a slug and they've got wings, but boy, they can pack a seriously painful sting.
03:33Glaucus atlanticus, otherwise known as blue sea dragons, are one of the more underestimated invertebrates in the Blue Deep.
03:40While they're harmless on their own, they have the ability to consume and utilize the venomous stinging cells found in other species as their own defense mechanism.
03:48Venomous blue dragons feed on Portuguese man o' war.
03:51The tiny organism also concentrates the substance, making it even more potent than their prey's original venom.
03:57This causes extreme suffering to anyone that comes into contact with them,
04:02resulting in unsavory symptoms like hyperpigmentation and vomiting.
04:06And that's why we ask people to, you know, if they get stung badly, they need to call the doctor. Maybe you can go to the hospital.
04:13The effects of their sting, combined with the blue sea slug's tendency to blend into the water's surface, has made them a truly insidious threat.
04:21Number 26. Stichodactyly.
04:24These seemingly unassuming organisms are proof that one species' ecological ally is another's anemone.
04:30So just then the sea cucumber looks over the mollusk and says, with fronds like these, who needs anemones?
04:36AAAAAAAH!
04:37These stichodactyla are primarily known for housing families of clownfish and protecting them from predators.
04:43But that doesn't mean they're helpful to all living beings.
04:46Some species are extremely noxious,
04:48and people that accidentally touch them have been subject to horrific effects.
05:03Some have been known to cause extreme reactions like anaphylactic shock and even liver failure,
05:08both of which require immediate medical attention.
05:10What's even scarier is that most sea anemones can't really harm humans,
05:14meaning someone could brush against a treacherous one without even realizing it.
05:19That alone is enough reason to avoid them completely,
05:21lest you want to take an impromptu trip to the emergency room.
05:25Number 25. Blue-spotted ribbon-tailed ray.
05:28While we'll be discussing stingrays in general in another entry,
05:32these brightly colored species are particularly beloved,
05:35with people across the world continuing to attempt their domestication despite the lack of success in home aquariums
05:41and the creature's ability to pack a punch.
05:44The blue-spotted ribbon-tailed ray may be small and shy by nature,
05:47but if threatened, they can dole out a harsh sting using the serrated spines on its tail.
05:53Their vibrant coloring may serve as a warning sign to most predators,
05:57but many humans still try to catch them for their home aquariums,
06:00increasing the odds of them being stung.
06:06If and when they are, the victim is treated to extreme pain
06:10and a dose of powerful toxicant that's fatal to humans.
06:14Despite the risks, they're still highly sought after by enthusiasts,
06:18proving that some will prioritize a hobby over their own health.
06:22Number 24. Sailfish.
06:24One look at this imposing critter should be all you need to keep a respectable distance.
06:33Known for their uniquely shaped bills and ability to reach high speeds,
06:37sailfish are one of the most evolutionarily advantaged marine creatures.
06:41Most will avoid humans should they randomly come across them.
06:44However, that dynamic changes as soon as they feel threatened or trapped.
06:49When caught on a fishing line, they will do whatever necessary to free themselves.
06:56In one instance, an elderly woman was stabbed, resulting in her being hospitalized.
07:02Considering the speeds they can reach,
07:03they can easily get caught without someone realizing they were even there.
07:07And if handled incorrectly,
07:09they can single-handedly ruin both the day and the trip all at once.
07:14Number 23. Crown-of-thorns starfish.
07:17While it may seem unassuming, the crown-of-thorns starfish is anything but.
07:33Their spines are infused with a toxin called asterosapinins,
07:37and the toxic spinal tissue can be easily absorbed into wounds.
07:40When this occurs in people, it causes periods of intense pain,
07:45bleeding, and swelling that can last for over a week.
07:47As if that weren't enough, the spines containing the substance can come off
07:51and become embedded inside a cut, with surgery being the only way to remove them.
08:01To make matters worse, their numbers have spiraled out of control,
08:05resulting in heightened injuries and the destruction of coral reefs,
08:08making them one of the most insidious forms of marine life living today.
08:12Number 22. Lionfish.
08:15These brightly colored fish have earned a reputation as being a hazard to humans,
08:19and are known as an extremely invasive species,
08:22making them one of the most ecologically harmful fish around.
08:26You have an animal that, once it invades,
08:28can really increase in population numbers very rapidly.
08:32With sharp spines lining its body,
08:34all it takes is a single touch of these venomous fin rays to bring about some truly nasty results.
08:40The symptoms range in severity, from the sensation of pins and needles to heart failure.
08:45While most healthy people will eventually be fine following some form of care,
08:57the elderly or extremely young are in more danger of perishing.
09:01With certain lionfish being so invasive, the chance for injury has increased,
09:06but hopefully efforts to reduce their population will help keep harm to humans down too.
09:11Number 21. Striped Pajama Squid.
09:14These cuttlefish are adorable, but that's the last thing you'll want to cuddle.
09:25Both venomous and poisonous, the striped pajama squid has the best of both worlds
09:30when it comes to defending themselves against various predators.
09:33They're infused with a toxic slime they can secrete if they feel threatened,
09:36harming their attacker long enough for them to escape.
09:45While it's unknown just how threatening the substance is to humans,
09:51the bright markings all over its body are enough indication that the striped dumpling squid should
09:55be avoided at all costs, whether you're actively hunting them or just happen to come across them.
10:01Number 20. The Portuguese Man O'War.
10:04The Portuguese Man O'War may look like the most deflated straggler from a bunch of balloons,
10:09but it stings like a swarm of bees.
10:12Even when they're washed up and they appear dead,
10:14the stinging cells in their tentacles are still active.
10:18Normally, they float along the ocean surface, paralyzing any fish that happens to wander
10:22too close to their tentacles and dragging them into their mouths.
10:26Lucky for you, humans are usually too big to get tangled up and paralyzed.
10:31But that doesn't mean getting stung won't hurt. A lot.
10:35Stings from a Man O'War's tentacles can leave long red welts, and in extreme cases,
10:40they can cause something like an allergic reaction that can close up your throat or
10:44send you into shock. All but the most severe stings are survivable,
10:49but they definitely do not sound fun.
10:52Number 19. The Stonefish.
10:55You thought stepping on Lego was bad? This small breed of fish has an unusual look.
11:00It resembles a rock bed, which is pretty useful for warding off predators.
11:04Its warty, bumpy skin is nearly indistinguishable from the sand and coral surrounding it.
11:10Unfortunately, those who accidentally tread upon the stonefish will be greeted with sharp
11:14fins that can pierce through shoes. On top of the initial painful sting,
11:25victims also have to contend with a neurotoxin that can shut down their respiratory system
11:30and even cause their heart to fail. Yikes.
11:33Found in the Indo-Pacific area, the stonefish is a delicacy in some places.
11:38After cooking has destroyed the venom, that is.
11:41Number 18. The Flower Urchin.
11:44Unlike the other toxic, hacky sack-like creatures in their family,
11:48flower urchins look less pointy and more squishy than their relatives. But they're not.
11:59They're covered with spines and little round feelers on stalks that look just like,
12:03you guessed it, a bouquet of flowers. But do not smell them.
12:07When those little blooms sense a threat, they clamp shut and inject an incredibly painful toxin.
12:13They can even break off little pieces of themselves, which are basically the claws
12:17of what's known as the pedicellariae, to get stuck in your skin and keep pumping it into you for
12:23hours. There have been alleged reports of urchin encounters having fatal consequences,
12:28but fortunately, no cases have been definitely confirmed.
12:32Number 17. The Shortfin Mako Shark.
12:35This is not a face you'd want to kiss. Not if you want to keep your lips in one piece anyway.
12:40Mako sharks are known for their jagged grins and their unbelievable speed.
12:49Reaching speeds of over 60 miles per hour, they're basically living torpedoes. You'd think
12:55that would make them pretty dangerous, and you'd be right. Although, let's be honest,
12:59just about anything faster than a flounder can out-swim most humans.
13:03Shortfin makos have only been responsible for one confirmed fatality out of a total of
13:08nine reported attacks. This suggests they're probably not that interested in taking down
13:13humans. In fact, many of those injuries historically happen when sport fishermen
13:21go after them. So, it's pretty hard to blame the sharks.
13:26Number 16. The Blue-Ringed Octopus.
13:29Oh, look at that bright, bright color change. Gorgeous!
13:32Such a pleasant name for such a debilitating beast. In regards to killing power,
13:36the blue-ringed octopus's claim to fame is its infusion of the neurotoxin TTX,
13:41or tetrodotoxin, into its bites. But what makes them so toxic? Well,
13:46the cool thing is that they don't make their own venom. They use other organisms,
13:50bacteria they find out here, and they hide them in their salivary glands.
13:53Humans in particular face the risk of TTX shutting down their respiratory system,
13:57which can mean death for those without immediate medical attention.
14:01Considering that one blue-ringed octopus contains enough TTX to kill up to 26 humans within minutes,
14:08and that TTX is thousands of times more potent than cyanide, the threat here is potent.
14:14Within only a fraction of a second, the octopus bites back and the scorpionfish spits it out.
14:21The scorpionfish will have a sore mouth for days, if it even survives.
14:2615. The Orca, aka Killer Whale
14:30Let's get one thing straight. There has only ever been one documented instance of a human
14:34being bitten by a wild orca, and no recorded fatalities. That being said, they're bigger
14:40than great white sharks, highly intelligent, and known to employ pack-hunting tactics on prey,
14:46ranging from seals to larger whales. For sheer size, strength, and smarts,
14:51orcas rate among the most effective predators in history.
14:56They're even known to team up to use waves as ranged weapons to knock prey off of ice flows,
15:09which pretty much sounds like one step removed from an actual comic book superpower.
15:20We can tell orcas are not interested in eating us because if they were,
15:24none of us would ever get back out of the ocean.
15:2714. The Sea Lion
15:29Some species of sea lion can weigh anywhere from 600 pounds to a full ton. The good news for humans
15:35is that sea lions mostly eat fish, so you're probably not on the menu. But that doesn't
15:41mean you can relax just yet. Sea lions can also get fiercely territorial. On rare occasions,
15:47that has resulted in them biting humans and even yanking them into the water.
15:51While that definitely sounds like a terrifying experience,
15:54sea lions are like orcas in that they don't seem that interested in attacking us.
15:59If they were, those huge teeth and a top swimming speed of 25 miles per hour would
16:04mean we'd hardly stand a chance. 13. The Leopard Seal
16:16Leopard seals have been aggressive to humans on several notable occasions.
16:21Normally, they eat krill, other seals, and the odd penguin. But there are several records of
16:34them chasing Antarctic explorers across the ice or even dragging them underwater.
16:44In 2003, one managed to drag down a snorkeling biologist, who sadly did not survive. Luckily
16:51for most of us, leopard seals live in the waters off the coast of Antarctica. So unless you're one
16:55of the few people who travel there for research, you're never likely to run across one. Still,
17:00if you ever visit, be sure to stay away from the edges of the ice.
17:04They like to shoot up out of the water and surprise their prey there.
17:1012. The Moray Eel
17:12Found most often in oceanic or brackish water, moray eels typically avoid contact with humans
17:21whenever possible. When sufficiently threatened, though, these creatures ensure their aggressors
17:26get what's coming to them. And more. Moray eel bites can produce easily-infected wounds.
17:42On account of the eels having a large amount of bacteria in their mouths.
17:45And that's not getting into their ability to chase down and kill other fish with minimal effort.
17:50Small sharks have even fallen victim to their attacks. Whoever said the electric eel was the
17:55only threatening eel around? 11. The Great Barracuda
18:11Fast, vicious, and capable of incredible injury. That is a frightening combination.
18:17With some recorded as growing almost as long as 7 feet, giant barracuda are also known for
18:23being quick swimmers. And for being keen on brutal ambushes. They lie in wait before charging forth
18:40and biting down on their prey. Armed with teeth sharp enough to damage nerves and blood vessels.
18:52As if that wasn't enough, a number of barracuda have ciguatera toxin in their flesh.
18:57Which can leave victims with nausea, hallucinations, and other side effects.
19:0110. The Needlefish
19:04Needlefish present an unorthodox kind of danger. They're not big enough to eat humans. They're
19:09not poisonous. And they don't get mad at us for territorial reasons. Nope, they're just long,
19:15sharp-faced fish who are extremely curious about the lights in our boats at night.
19:29So curious that they'll shoot across the shallows at 37 miles per hour and
19:34leap out of the water to see what's going on above decks. For the people on deck,
19:38that means a sudden barrage of fishy spears that fly out of the deep like the first shots
19:42of a war with Atlantis. Injuries can range from bites and scratches to pointy wounds
19:51if the fish's beaks hit you hard enough. 9. Stingrays
19:55It may seem passive, but don't dare underestimate it. The stingray, typically relaxed, can hold its
20:02own and even do serious damage with its sharp spear-esque tail. Stiffening whenever the ray
20:07detects a threat, the tail possesses a serrated tip capable of severing arteries and is lined
20:13with venom that particularly endangers mammals. The stingray's sheer deadliness was tragically
20:26shown when, in 2006, wildlife expert and television host Steve Irwin, also known as
20:31the Crocodile Hunter, was killed by a stingray's tail repeatedly striking him in the heart.
20:378. Bull Shark This might be a list of deadly ocean creatures,
20:42but bull sharks are actually at their most dangerous when they're not in the ocean.
20:48Now, don't completely freak out. Sharks haven't figured out how to come on land...yet.
20:53But, bull sharks do swim inland, up rivers, and into lakes.
21:00Like most sharks, bull sharks aren't all that interested in humans as prey.
21:04But, they're big enough that a curious nibble will put you in the hospital. Thanks to that
21:09increased proximity, bull sharks have attacked more humans than any species other than great
21:14whites or tiger sharks. They've harmed over 100 people and taken the lives of about 25.
21:217. Cone Snail Snails are soft, squishy, slow-mo
21:25creatures that eat leaves and carry their little houses on their backs. How the heck do they end
21:30up on a list of deadliest creatures? Well, these snails are here for the venomous, harpoon-like
21:36tooth they use to hunt their prey. Yes, venomous harpoons. It's a cartoonishly
21:42evil-sounding weapon, sure, but it's also deadly serious.
21:49Geography cone snails, in particular, are the most venomous animal in the world,
21:54full stop. At least 30 people have had fatal interactions with cone snails.
21:59But the nature of being a dangerous animal that hides in a pretty shell on remote beaches
22:03means they could be responsible for even more fatalities we don't know about.
22:186. The Tiger Shark The bull shark may be imposing,
22:22but the tiger shark is something else. This large shark has a reputation for attacking and eating
22:34anything, including smaller sharks, and is one of the sharks most frequently associated with fatal
22:40shark bites. Tiger sharks don't seek out humans as food, but they do tend to linger in shallow
22:48waters and river mouths where contact with humans is most likely. What's worse, their keen senses
23:00and calcified teeth allow them to make quick work of any prey they desire.
23:055. The Great White Shark The adjective great being in this animal's
23:12name is less a statement of positivity and more a grim tribute to its ferocity.
23:19The great white shark's most immediately recognizable quality is its size. They can
23:28grow to over 25 feet in length and weigh over 7,000 pounds. However, these sharks have another
23:35notable habit. They strike at their prey from below with their mouths wide open,
23:40allowing their razor-sharp teeth to do as much damage as possible.
23:49It's no wonder that about a fifth of attacks by great white sharks are reportedly fatal,
23:57given the viciousness on display.
23:594. Saltwater Crocodiles Fear the crocodile, for it strikes when you
24:15least expect it. As the name suggests, the saltwater crocodile can very easily traverse
24:20open waters, allowing them to spread across Southeast Asia with terrifying ease. Saltwater
24:30crocodiles have been reported to have a bite power ten times greater than that of the great
24:34white shark. At the very least, its large size and weight make it frighteningly easy to trap its prey.
24:46During a battle in World War II, hundreds of Japanese soldiers crossing through swampland
24:50in Myanmar were allegedly killed by saltwater crocodiles. Stuff like this gives us pause.
25:033. The Oceanic Whitetip Shark As we've repeatedly stressed, sharks usually
25:10are not interested in eating people. But there's one time when the normal rules do not apply,
25:15a feeding frenzy. When there's blood and commotion in the water, certain species,
25:20like the especially aggressive oceanic whitetip, go into a swarm. And what causes more blood and
25:26commotion than a shipwreck? There have only been a handful of confirmed fatalities from
25:31whitetip shark attacks, but many shipwrecks and most castaways go unreported. If other wrecks
25:37played out like that of the USS Indianapolis in World War II, we may never know how many
25:41human lives the oceanic whitetip has taken. But in the Indianapolis wreck alone, the estimated
25:47count was somewhere between a dozen and 150. 2. The Box Jellyfish
25:53When it comes to the dangers of the sea, size matters not. Hence,
26:09we have the box jellyfish, a class of jellyfish that compensates for its small stature
26:14with a largely unparalleled sting.
26:23Those subjected to the venomous touch of the box jellyfish's tentacles are said to undergo
26:28extreme pain and a burning feeling. Box jellyfish venom is reportedly so potent
26:34that some people experience fatal cardiac arrest within minutes of being stung.
26:38The worst part is how hard it is to detect a box jellyfish before it can cause harm,
26:55due to its almost transparent appearance.
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27:141. The Sea Snake
27:24And here we thought ordinary snakes had enough deadly surprises to offer the world.
27:28Alas, the sea snake, though typically nonchalant when it comes to other animals,
27:32still poses a danger thanks to its venom.
27:41On the rare chance that a sea snake or coral reef snake chooses to inject its toxin while
27:46biting a perceived attacker, a sizable list of symptoms are in store for the target.
27:51The after-effects range from elements of nausea to general aching and a tetanus-like
27:56ailment to even heart failure. It's a horrible fate delivered from an otherwise passive animal.
28:02As one group of hunters searches the reef, they're joined by the other.
28:07Which of these aquatic creatures would you be the most scared of coming across?
28:11Let us know in the comments below!
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