Venomous Marine Animals

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The sea may be a place to have fun. But it also is home to a number of dangerous marine animals who never really attack but could be fatal if they come in contact with you accidentally. There is a saying that

 “what you do not know, you do not touch”

Marine organisms that look the prettiest are at most times the deadliest. There are few common marine organisms that pose a threat to humans because of their effective defense mechanisms that we should generally be aware of. Some of these organisms are normally found in deeper waters but there are few that are found near the inter-tidal zones.

Sea Urchins


Sea urchins are also called sea hedgehogs which they resemble. They are small, spiny animals. About 950 species of sea urchins exist that inhabit the ocean from the inter tidal zone to around 5,000 meters deep.  Common colors include black and dull shades of green, olive, brown, purple, blue, and red. Sea urchins move slowly, feeding primarily on algae. Sea urchins are non-aggressive and relatively slow-moving and do not pose a threat unless you accidentally come in contact with one.

Like most aquatic life injuries, sea urchin injuries are caused by the animal trying to defend itself. Sea urchin’s spines are its first line of defense. The length and sharpness of an urchin’s spines vary from species to species. Some species have stubby, blunt spines while other species have long, sharp, venom-filled spines.



Lion Fish

The red lion fish (Pterois sp.) is a venomous fish found normally in coral reefs. They are normally found near the bottom or in crevices.  It has large, venomous spines that protrude from the body similar to a mane of a lion, giving it its name. No definitive predators of the lion fish are known hence it is considered an invasive species in few countries. The spines are the lion fish’s first line of defense. However, its sting is usually not fatal to humans. Envenomed humans will experience extreme pain, headaches, vomiting and breathing difficulties. A common treatment is soaking the affected area in hot water.





Stone fish

Stone fish are venomous, dangerous, and even fatal to humans. It is one of the most venomous fish known. They are found sometimes in inter tidal regions and camouflaged in coral reefs. It has potent neurotoxins secreted from glands at the base of their needle-like dorsal fin spines which stick up when disturbed or threatened. The vernacular name of the species, the stone fish, derives from the ability to camouflage itself with a gray and mottled color similar to the color of a stone. Swimmers or divers may not notice them, and may inadvertently step on them, triggering a sting. When the stone fish is disturbed, it may inject an amount of venom proportional to the amount of pressure applied to it. So always keep a lookout where you put your hands and feet.





Jelly fish

Kovalam Marine life

Jellyfish are not fish but are closely related to corals and anemones (known collectively as cnidarians which literally means ‘stinging creatures’). All possess stinging cells which are used to capture prey. Jellyfish are the free-floating forms of cnidarians. Jellyfish are composed mainly of water and absorb oxygen directly from the surrounding water. Their tentacles range from 1 cm to 36 meters in length and contain hundreds of thousands of nematocysts. The bell does not contain stinging cells. Nematocysts can still sting even when the tentacles are severed from the jellyfish so beware of touching jellyfish washed up on beaches or broken tentacles floating in the water. Most varieties of jellyfish stings are harmless to humans. Species like sea wasps, Portuguese man of war, etc., are the deadly ones.



Sea Snakes

Sea snakes are reptiles, have scales and flattened, paddle-like tails as well as one long continuous dorsal fin. All sea snakes are highly venomous and should not be handled even though they are shy, gentle and do not normally pose a threat unless provoked. The most common sea snake is your Banded Sea Krait that is found in most Indo – Pacific reefs. When they do bite, venom is injected. Most victims bit by sea snakes are fishermen trying to remove them from their nets and swimmers that accidentally come in contact with these snakes. Sea snakes may approach divers out of curiosity. The best defense is to stay calm and not lash out at the snake and it will soon continue on its way. Like other reptiles, they breathe air and have to periodically return to the surface. They are usually found in depths between 5 to 10 meters hunting for food on the seabed or coral reef.


Cone Shells

Cone shells are highly sought after specimen by shell collectors due to their attractiveness. They can be found during low tide in inter tidal regions in tide pools and particularly at night when they come out to feed, which makes them easily accessible.

Behind this attractive marine animal outlook is a highly venomous harpoon which is used to paralyze prey, typically fish, mollusks or worms, before drawing it back to their mouths. The venom is contained in the tongue-like proboscis equipped with harpoon-shaped teeth. The harpoon can be fired numerous times if needed and with such force that it can pierce wet suits and clothing. Many human victims get stung when they carry them in pockets or in mesh bags close to the body. The venom contains neurotoxins which cause weakness, loss of coordination and in serious cases, respiratory failure.





To learn more about marine life, Please do check out our Outdoor Science Field Trip page