Open Tomorrow : 10:00AM - 05:00 PM

  • Monday : 10:00AM - 05:00 PM
  • Tuesday : 10:00AM - 05:00 PM
  • Wednesday : 10:00AM - 05:00 PM
  • Thursday : 10:00AM - 05:00 PM
  • Friday : 10:00AM - 05:00 PM
  • Saturday : 10:00AM - 05:00 PM
  • Sunday : 10:00AM - 05:00 PM

Top 7 Most Poisonous Water-Dwelling Creatures

There’s no two ways about it: our planet is a dangerous place.

In order to survive in hostile habitats, some marine creatures have developed defence mechanisms that are much more direct and deadly than paws and claws. So next time you’re frightened of a tiny house spider, remember that there are far scarier things at sea.

Puffer Fish

It can kill an adult human in: Anywhere between 20 minutes and 24 hours

Don’t be fooled by this fish’s cute appearance: it’s actually quite dangerous! Most puffer fish swim in the waters surrounding Mexico, China, the Philippines, and, of course, Japan – where the meat of some puffer fish is a delicacy. The skin and certain organs (including the gallbladders and livers) of many puffer fish species are highly poisonous to humans – they are known to have caused rapid and violent deaths.

Marbled Cone Snail

It can kill an adult human in: Hours

The marbled cone snail actually contains painkilling compounds that are 10,000 more potent than morphine (minus the additives), but it also carries a venom so strong it can instantly paralyse a human. As if that’s not terrifying enough, there is also no anti-venom – which means surviving an encounter with one of the deceptively beautiful snails is down to pure perseverance and luck.


It can kill an adult human in: Under an hour

Divers beware: this venomous fish can disguise itself with its camouflaged appearance and can easily blend in with rocks on the seabed! This fish’s dorsal area is lined with 13 spines that release a venom that can cause swelling, necrosis of tissue, paralysis, shock, and ultimately death.

Belcher’s Sea Snake

It can kill an adult human in: 30 minutes

Despite having venom that’s 100 times deadlier than most of its terrestrial relatives, the Belcher’s sea snake is actually a very docile sea species. It rarely attacks without provocation, and even when it does, it doesn’t always penetrate a diver’s wetsuit or release all its venom. However, its venom does have the power to kill in 30 minutes – just a few milligrams of this toxin would be enough to kill over 100 men.

Blue-Ringed Octopus

It can kill an adult human in: Under 10 minutes

If any animal is ‘silent but deadly’, it’s the blue-ringed octopus. This cephalopod may be small (only the size of a golf ball) but its bite sure does pack a punch: its venom is powerful enough to cause blindness, nausea, paralysis and respiratory failure, as well as death. Plus, one of these moderate-sized creatures carries enough venom to kill up to 26 adults at once!

Poison Dart Frog

It can kill an adult human in: 5 minutes

The poison on this two inch-long frog is so potent, Colombian tribes have used it to tip their blowgun parts – hence its name. Fun fact: this amphibian species is not naturally poisonous (specimens raised in captivity and fed on fruit flies and other common insects don’t develop toxicity) and it’s speculated that it picks up various poisons from plants in its natural habitat.

Box Jellyfish

It can kill an adult human in: Under 5 minutes

The box jellyfish is the worst animal you can come across on this list, as it’s believed to be the most poisonous animal in the sea. This deadly creature is so transparent that it’s almost invisible if you’re not looking out for it. The venom of this silent killer is so overpoweringly painful, victims either go straight into shock and drown or die of heart failure before they can swim to shore.

Here at Blue Reef Portsmouth, you’ll discover some of the most fascinating creatures that lurk beneath our oceans and have the opportunity to learn all about them! For more information, call us on 023 92875222 or email us on [email protected]

Get Blue Reef Aquarium Portsmouth news and offers right to your inbox!