Over 70% of the Earth’s surface is covered by oceans. They drive weather, regulate temperature and are a vital source of sustenance, commerce, transport and growth. Without oceans, we wouldn’t exist.



But despite our dependence on oceans, we know very little about them. If you think about it, most of our time is spent ON oceans, not in them. We surf, take cruises, go on whale tours, fish and swim, yet humans have only actually explored 5% of the world’s oceans. Scientists have discovered 230,000 marine species, but there are 2 million more we still have to find.



So if you think these 10 creatures are scary, what's undiscovered is probably much, much worse.

Box Jellyfish

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The box jellyfish is said to kill more people each year than any other marine animal. Its deadly toxins affect the heart, skin and nervous system and are so powerful and painful that most human victims never make it back to shore, either dying of heart failure or drowning due to shock. If they miraculously survive, they’ll be in pain for weeks and physically scarred for life.

Puffer Fish

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Puffer fish are super cute and all, but one fish contains enough poison to kill 30 humans! They contain a foul-tasting substance called tetrodotoxin, which is 1,200 times more poisonous than cyanide. But even though they’re considered to be the second-most poisonous vertebrate in the world, their meat is still a delicacy. Chefs go through extensive training to learn how to remove all of the toxic parts and not contaminate the meat, but over 20 people die each year from consuming improperly-prepared puffer fish.

Great White Shark

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Great whites are the most famous predator for a reason. Their mouths are lined with rows and rows of serrated, triangular teeth that are perfect for ripping off large chunks of flesh. They’re also the largest predatory fish, growing to a length of 6 metres, and have an exceptional sense of smell to detect prey. Great whites feast mostly on seals, sea lions and small whales, but they occasionally munch on humans. In the past 10 years, there have been at least 66 documented attacks.

Striped Surgeonfish

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These beautiful fish don’t attack, but the sharp spines near the base of their tail are extremely poisonous. They become erect when the fish senses danger and are so sharp that they can produce deep gashes on the attacker. Surgeonfish have even been known to cut through wetsuits! The wounds are extremely painful and great care must be taken to completely remove the poisonous spines from the skin.

Barracuda

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Barracudas are master predators. Their long, sleek bodies allow them to swim up to 40 km/hr (25 mph) and overtake their prey with short bursts of speed. Attacks on humans don’t happen often, but thanks to the barracudas razor-sharp teeth, if you encounter one you’ll probably end up losing an arm or a leg. If you’re fish, however, you don’t stand a chance. Barracudas are voracious, opportunistic hunters that aren’t choosy—they’ve even been known to eat their own young.

Indian Needlefish

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Needlefish are sleek, slender little fish that range from 3 cm to 95 cm in length. They have long, narrow jaws filled with sharp teeth and, depending on their age, eat everything from plankton to fish. Their danger to humans lies in their body shape. Needlefish swim close to the surface and are capable of jumping out of the water at 61 km/h (38 mph). They prefer to jump over boats than swimming around, and they’re especially attracted to artificial boat lights at night. Fisherman have reported being impaled by schools of needlefish, resulting in deep puncture wounds. And in 2007, a young boy was stabbed in the heart by 6-inch needlefish beak while night diving.

Yellow-Bellied Sea Snake

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Yellow-bellied sea snakes have 1.5 mm fangs and only inject a tiny dose of venom, but that doesn’t mean they aren’t dangerous. Their venom contains incredibly high levels of neurotoxins and myotoxins, and a bite will result in muscle pain, stiffness, drowsiness, vomiting and drooping eyelids. If the bite is a bad one, it can lead to paralysis and death.

Fire Coral

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Fire coral isn’t actually coral. It’s really made up of tiny marine organisms related to jellyfish that have invisible tentacles armed with nematocysts. These venomous cells cause excruciating pain, and if a large area is affected, the victim will experience nausea and vomiting.

Cone Snail

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Cone snails are predatory sea snails with painful harpoons. People often pick them up because they’re so pretty, but after spending a few seconds in their captors’ hands, they fire their harpoon. Large species can penetrate through skin, gloves and wetsuits, and more serious stings will result in paralysis, changes in vision, respiratory failure and even death. The only treatment is life support.

Blue Ringed Octopus

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This octopus only grows to be 12 to 20 cm (5 to 8 inches), but its venom is 10,000 times stronger than cyanide and can easily kill a human. It causes total body paralysis that lasts a few hours but leaves the victim conscious, alert and unable to call for help. The only treatment is to undertake rescue breathing until the toxin is metabolized.