The Most Dangerous Animals in the Sea

Stingrays possess venomous tail spines, which can end in deadly consequences for humans if engaged.

16. Moray Eels

A moray eel in the Black Sea.

Moray eels include a family of almost exclusively marine eels found in the sea. The largest among them is the slender giant moray (Strophidon sathete) which can attain a length of 13 feet. Moray eels are often considered to be ill-tempered and vicious in nature. In truth, these eels tend to shy away from humans by hiding in rock crevices in the ocean. Most attacks by moray eels on humans have been reported to occur when divers have disturbed their burrows to which they react fiercely or when divers try to hand-feed them in order to attract tourists. The fact that a number of divers have lost their fingers in the process has forced the concerned authorities to ban such eel-feeding practices. The bite of the eel is primitive in nature and so powerful that it cannot be removed and must be manually pried off. It is also believed that a few species of eels are venomous in nature. Some eels that feed on toxic algae can result in human death if they are consumed by humans.

15. Toxic Pufferfish And Boxfish

Pufferfish and boxfish are both members of the order Tetraodontiformes. The pufferfish produce a deadly neurotoxin called the tetrodotoxin in their internal organs and skin. The highly potent toxin is capable of killing humans easily. The toxin is actually produced by several bacterial species living as parasites in the body of these fishes. The tetrodotoxin damages the firing of action potentials in nerves, which prevents the nervous system from carrying messages to the muscles for movement. Inhalation, ingestion or injection or contact with abraded skin allows the toxin to enter the victim’s body. The pufferfish’s internal organs contain sufficient poison to result in the death of the consumer by respiratory failure. Similar to pufferfish, boxfish also contains tetrodotoxin that is poisonous to eat.

14. Surgeonfish

There are about 75 species of surgeonfish inhabiting the oceans of the world. As their name suggests, these fish possess scalpel-like, movable spines at the base of their tail on each side. The spines allow the fish to defend themselves and can easily slash a human hand that comes accidentally near the fish. However, the fish generally are not aggressive by nature and thus unpleasant contacts with human are rare.

13. Barracudas

Barracudas are long and lean fish who are experts at hunting. The sleek body of the fish allow them to move at speeds of about 40 km per hour. Barracudas show no mercy to their prey, shredding the prey to pieces before devouring them using their razor-sharp teeth.

12. Triggerfish

A big triggerfish species, as evident from its name, the titan triggerfish inhabits the reefs of the sea at depths of up to 160 feet. Although the fish tend to avoid snorkelers and divers, the female aggressively attacks anyone posing a threat to its nest during the nesting season. The fish build their nests in a cone-shaped sandy area and anyone who accidentally approaches this territory is on for a big shock. The bites of the titan triggerfish are not poisonous but sharp enough to cause serious injuries demanding immediate medical attention. Divers are thus advised to swim horizontally away from such nests.

Another species of triggerfish, the Yellowmargin triggerfish is also capable of sharp bites and must never be approached while tending to eggs.

11. Textile Cone Snail

The gentle-looking snail is actually one of the most toxic creatures of the sea. The textile snails have hollow teeth through which they inject a lethal venom into their prey. Mollusks are the most common prey of these snails but sometimes they turn to consuming their own kind when meals are scarce.

10. Indonesian Needlefish

The Indonesian needlefish can be observed schooling near the surface of subtropical and tropical waters of the world’s oceans. At times, these fish hurl themselves out of the water and once airborne, they can act like dangerous flying daggers that might hurt anything coming their way. Although extremely rare, human fatalities and injuries triggered by these fish have been reported. In most of these cases, the victims were stabbed by the sharp and elongated jaws of the Indonesian needlefish. Boatmen at night are particularly vulnerable to such attacks since light from the boats have been known to attract the fish.

9. Scorpionfish

A yellow scorpionfish.

Scorpionfish are a family of marine fish that includes a large number of venomous species. The fish have sharp spines coated with venomous mucus. They can be dangerous to divers who approach them too close and come in contact with the venomous spines of the fish.

8. Crown-of-thorns Starfish

The crown-of-thorns starfish is a large starfish species that is named after the venomous thorn-like spines covering its upper surface that resemble the biblical crown of thorns. If the venom comes in contact with human skin, it might result in a highly painful wound and even paralysis.

7. Fire Corals

Fire corals are colonial marine organisms that are more closely related to Hydra and other hydrozoans than to true corals. These corals are distributed widely in the tropical and subtropical waters of the world. They grow on rocks and coral in the form of brush-like growths. Accidental contact of divers with these corals is common. If the divers are stung by the corals, it causes intense pain that can last for two weeks.

6. Stonefish

Stonefishes are fishes of the family Synanceiidae. These fishes are quite dangerous to humans as they have the ability to remain well camouflaged in their habitat. They are also venomous in nature. The spines on the back of these fish are powerful enough to be able to penetrate through a rubber soled shoe and their venom might prove fatal to humans. For example, the fish of the Synanceia genus have potent neurotoxins that are secreted from glands located at the base of the dorsal fin spines of the fish. The gray, mottled color of the fish allows it to easily blend with the stones on the sea floor. A swimmer, unaware of its presence, might accidentally step on it and receive a sting that delivers venom into the swimmer’s body. The venom is potentially lethal and triggers excruciating pain in the victim. Application of heat to the stung area and application of antivenom in extreme cases might be needed. Stonefish stings can also happen on the beach since these fish are known to survive for about 24 hours without water and thus might remain hidden in the boulders at the beach.

5. Portuguese Man o' War

A Portuguese Man o' War in Florida, USA.

The Portuguese man o' war (Physalia physalis) is a marine creature that appears like a jellyfish but is not one. The organism is a marine hydrozoan that is actually a colonial organism where several polyps remain attached to each other and are unable to survive alone. The creature has tentacles that are venomous in nature and can deliver a painful sting that might also prove fatal.

4. Stingrays

Stingrays are cartilaginous fish that belong to the suborder Myliobatoidei and are classified into eight families. Most stingrays are armored with one or more barbed stingers on the tail that aids the stingrays in self-defence. The stingers are about 13 inches in length. The undersides of the stingers possess two grooves with venom glands. The stingers are covered by the integumentary sheath where the venom remains concentrated. When humans come uncomfortably close to stingrays, the latter might inflict severe wounds on the human using its stingers as an exhibit of self-defence.

3. Salt Water Crocodiles

Saltwater crocodiles are the largest crocodilians in the world and can attain lengths of up to 23 feet and weigh as much as 2,204 pounds. Despite their massive size, the crocs can easily remain hidden and strike when their prey comes dangerously close to them, taking the prey by complete shock, and allowing little time for the prey to escape their deadly jaws. A large number of human fatalities also happen each year due to attacks by saltwater crocodiles on humans.

2. Tiger Shark

The tiger shark is a large macropredator found in many tropical and temperate seas across the world. The shark is noted for having the widest prey base among all shark species. It is a solitary and nocturnal hunter by nature. A large percentage of fatal shark bite incidents in human cases have been associated with this shark species. The tiger sharks often visit harbors, canals, river-mouths and reefs near the coast, increasing the chances of encounters with humans. Although they are the apex predators in the ecosystem they inhabit, the sharks are occasionally hunted by killer whales. They have also not been spared by humans and are a near threatened species due to extensive finning activities and improper fishing practices. 4,668 tiger sharks were also culled between 1959 and 2000 to protect the coastal tourism activities. Activities like cage diving with the sharks and feeding them are discouraged as they increase chances of human-shark conflicts.

Another species of shark, the Grey reef shark, is also known for its territorial and aggressive nature. Non-fatal attacks on humans have been reported.

1. Great White Shark

The great white shark.

The great white shark undoubtedly a master predators in its habitat and is also the apex predator that sits at the top of the ocean food chain. The fish can weigh 5,000 pounds and has been known to attain lengths of up to 20 feet. The sharks possess about 300 teeth which can easily tear apart the flesh of sea lions, sea turtles, and small toothed whales. One-third to one-half of shark attacks on humans are triggered by the great white. However, most of these attacks are unintentional and are rarely fatal.


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