The Dangers Of Scuba Diving: 10 Most Deadly Sea Creatures (Part I)

The Dangers Of Scuba Diving: 10 Most Deadly Sea Creatures (Part I)

The creatures you most want to avoid when scuba diving, swimming, or snorkeling.

The ocean is vast and safe but it also home to 10 of the planets most dangerous animals.

Whenever I do one of these articles, I always want to start out with a disclaimer: scuba diving is a very safe sport, and what risks there are, rarely come from sharks, moray eels and other aquatic life, but from human error.

That being said, there are certain animals that you might encounter under water that good sense would advise you to steer clear of.

Remember, touch nothing, leave only bubbles, take only pictures.

Which animals are the most dangerous one remains an ongoing debate, as it is hard to find data on the subject. Scientists often have to rely on the accounts from shocked eyewitnesses, who are rarely trained at marine life identification, often making their witness statements unreliable.

Do you know How To Become An Environmentally Friendly Diver?

But this list seeks, nonetheless, to outline 10 animals that are definitely among the most dangerous ones out there, based on available knowledge and not in any particular order.

Stone Fish

This fish, equal parts fascinating and appalling, makes the list because of its combination of being a master of camouflage and packing more deadly poison than any other fish in the sea.

They’re not aggressive and do not attack, using their poisonous stingers merely as defensive weapons. But because they blend in so well with rocky outcrops and coral reefs, humans find themselves inadvertently stung by them. Though such encounters are rare, they still rank as one of the most dangerous animals.

A stone fish blending in – Credit: Cigdem Sean Cooper

Blue-ringed Octopus

Small, but (potentially) deadly, these tiny, sand-colored octopi can be hard to spot, but pack a poisonous punch. They display their blue rings when they feel threatened, and if needed, can deliver a tiny, often painless, bite, which delivers one of the most potent poisons in any marine animal.

Here’s an interesting article about The Smart Octopus: Diving With Octopus.

Due to their diminutive size, they are often overlooked by humans, and their tiny bite if rarely felt, making it hard for rescue personnel to deduce what is causing a victim’s discomfort. Part of these creatures getting a most dangerous animal mention is due to this unknown villainy.

The small but dangerous blue ringed octopus – Credit: James van den Broek

Sea Wasp: actually the most poisonous creatures

Relative to its size the sea wasp, also know as the marine stinger, is the most dangerous creature in the sea. A member of the box jellyfish family, this tiny, translucent jellyfish is the most poisonous animal on the planet. It is small, squarish, and with tentacles coming from each “corner”. These can be quite long and hard to see, and a sting will cause severe pain, and very likely death in three minutes or less. Even though sea wasps aren’t aggressive, beaches along the Australian northern coasts are often closed during the sea wasp season.

Women’s panty hose, as it turns, are completely effective defensive measures tried, tested and proven by legion of Aussie lifeguards and surfers who brave the sea wasp season for the good waves. Wear some panties on your arms and legs and the tentacles won’t get you.

Cone Snail: the slowest of the most poisonous creatures

Yes, a snail made the list. Makes sense, if you think about it. After all, for a poison to be effective for a snail, it has to be really fast acting, otherwise its prey would swim away, out of reach of the slow moving slug.

The cone snail injects its poison, really a mix of several hundred toxins, via a harpoon-like tooth and a sting can kill a fully-grown human being. This, in spite of the fact that the snail itself is but a few inches long, with the largest of the species growing up to six inches.

What makes it even scarier is that no anti-venom exists for this animal’s poison.

Watch this video of a cone snail harpooning a fish.

Great White Shark: not the most dangerous animal

Truly the stuff of your Jaws-fueled nightmares, the Great White Shark is more than a thousand pounds of muscle, armed with hundreds of razor-sharp teeth.

Shark Series: The Great White Shark

They account for about two thirds of human attacks every year, though most aren’t fatal, and pretty much all are likely unintentional. This apex predator is an important actor in the oceans’ food chain, and more in need of protection from us, than us from it.

The great white shark shows razor-sharp teeth – Credit: Mogens Trolle

Tiger Shark

Along with the Great White, the Tiger Shark is one of the relatively few shark species that we as humans need to be cautious of. It is largely nocturnal, so normal beach-goers and swimmers are rarely in harm’s way. But divers doing night dives will want to keep their eyes peeled if they’re in an area that has known populations of them.

Shark Series: The Tiger Shark

Attacks have been reported, but as with all sharks, its reputation as one of the most dangerous animal is somewhat exaggerated, and plenty of divers have seen this magnificent hunter with no other consequences other than bragging rights and the thrill of the sighting. Still, displaying due diligence when around one is a good idea.

The nocturnal tiger shark – Credit: Michael Rothschild


The beautiful lionfish, a favorite among underwater photographers, is also quite a poisonous fish. Along its fan-like fins are stingers that pack a potent venom. Usually not fatal, it does carry quite a punch and can be very painful indeed.

For those who are allergic, it can be much worse, though, and even potentially deadly. Lionfish are seen both day and night, but as they are attracted by dive lights once it gets dark, showing a bit of caution when you do night dives is prudent, as these can be considered one of the dangers of scuba diving.

The not-so-fatal lionfish can leave a painful sting – Credit: Joshua Haviv

Sea Snake

A beautiful white and black striped animal, the sea snake lives in the Indio-Pacific. It is not an aggressive animal, so attacks are rare, but if they do attack, they have a poison that is potentially fatal. Since sea serpents have always captured our imagination and inspired fear, this poisonous creature makes the most dangerous animal cut.

The laid-back but poisonous sea snake – Credit: Paul Cowell


Stingrays are always a crowd pleaser on dive boats, and they come in all shapes and sizes, from the smallish blue-spotted one to the massive fan-tailed stingray. They are quite passive animals, who will remain in the same spot for as long as possible, and choosing flight over fight if a diver comes to close.

However, from time to time, for a scuba diver they could be a most dangerous animal. Divers could step on one while wading through shallow water while doing shore dives, or accidentally land on one if they sit on the bottom, which can prompt the animal to attack.

Common for all stingrays is the barbed stinger located on their tails, which, apart from being painful in itself, also packs a venom. The size of the stinger and the potency of the venom varies, from the blue-spotted stingrays stinger of a few inches, to the foot-long stinger of the giant river stingray.

Some incidents are also caused by divers trying to capture a stingray, which is how Australian TV show host Steve Irwin died.

Here’s the video of different, stranger stingray attack.


A list of the most dangerous animals in the oceans (or on land) wouldn’t be complete without the ultimate killer: us. To put this into perspective, sharks kill about 10 people every year, while people kill about 100 million sharks every year!

And the detrimental effects our industrialized fishing processes has had on pretty much every species of fish out there cannot be denied either. And while it may be tempting to negate this by saying that a most dangerous animal list should focus on creatures that are deadly to humans, do not underestimate the danger we pose to ourselves.

If we continue on our present course in the way we treat the oceans, we are heading towards a situation where the oceans will no longer be able to sustain us. And without the oceans, we won’t be able to sustain life on land, either. No ocean, no us. No blue, no green, as notes oceanographer Dr. Sylvia Earle says.


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