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6 of the Scariest Sea Predators

All around the world, the seas are filled with fascinating creatures of every colour, shape, and size, and you can find them everywhere from shallow waters all the way to the Mariana Trench. With such a diverse range of marine creatures, it’s no surprise that there’s some creepy crawlies and truly spine-tingling predators lurking in the sea.

Frilled Shark

Sharks have a rather patchy reputation when it comes to their fear factor, and although their representation as man-eating predators is largely undeserved, they are rather fearsome creatures. However, standard run-of-the-mill sharks are nothing compared to this species – frilled sharks make our zebra sharks at Blue Reef Aquarium Portsmouth look downright cuddly in comparison!

Admittedly, frilled sharks are rather weird-looking as opposed to scary, but you have to admit that there is something rather unsettling about their eel-like bodies and their 300 teeth spread across five rows. If you were hoping that these creepy creatures were at least pint-sized then you’re out of luck, because they can grow to five feet in length.

They have often been described as ‘sea serpents’, spurring plenty of myths over the years because these creatures are so rarely spotted in the wild. Since the frilled shark lives in the very depths of the ocean – they can dive down to depths of 5,200ft – scientists have not been able to properly observe their hunting patterns, but it’s believed that the shark kills its prey by constricting it (similar to a snake). Therefore, the frilled shark’s teeth seem to act more as a visual threat for prey.


Despite how cute and squishy our jellyfish look, they can be fierce predators, and a certain species are biologically immortal! Often referred to as ‘jellies’, because they’re not actually fish, these ocean predators are just as likely to feed on each other as they are to feed on small fish and crustaceans.

What makes jellyfish truly scary, besides their ability to regenerate in a science-fiction-worthy manner, is their toxicity. For example, the sea wasp – a type of box jellyfish – can kill an adult human in minutes with its venomous sting. If that wasn’t worrying enough, these fearsome creatures still have a nasty sting after they die. In 2010, pieces of a dead lion’s-mane jellyfish was reported to have stung 120 to 150 beachgoers in New Hampshire, USA.

Gulper Eel

As the name would suggest, gulper eels have a very specific feature that makes them scary: their disproportionately large jaws. It is these jaws which make some people refer to the eel as a ‘pelican eel’.

Although they are called eels, they are actually just really long and slim fish. Their jaws make up a quarter of their entire body lengths, and their stomachs can expand to accommodate large meals. Despite these incredible features, it’s believed that they mostly eat squids and small crustaceans, using their large mouths like a net. Gulper Eels can be found in tropical areas of the ocean, as well as some more temperate areas, although in North Atlantic waters they are known to live at a deeper depth of 9,800 ft.

Giant Squid

Giants squid are the closest existing sea predator we have to the mythical kraken, with females growing up to 43ft in size and the males reaching 33ft. They’re also cannibals, which makes them just as scary to their fellow squids as they are to us. They owe their size to a phenomenon known as deep-sea gigantism, which is a tendency for deep-sea invertebrates to grow considerably larger than those species living in shallower waters. Giant squid can be found in both the North and South Atlantic Oceans, but they tend to stay away from tropical and extremely northern areas. Thankfully, they prefer deep waters of up to 3,300 ft, so there’s no chance of one wrapping its tentacles around you on your next trip to the beach.

Sarcastic Fringehead

Sarcastic fringeheads look rather unassuming, until they’re threatened. If you make the mistake of bothering one of these incredibly territorial fish, you’ll be faced with its alien-like mouth. As an offensive tactic, fringeheads can open their mouths to four times their original size, scaring away any other predators (or particularly unlucky humans) with their intimidating size and colouration.

Fringeheads are usually a murky brown colour, which is what makes their offensive tactic so impressive, as they display a mouth filled with bright blues and neon yellows. They also use this manoeuvre to assert dominance over other fringeheads in territorial battles.


Thanks to their mesmerising appearance and venomous spines, these fish are just as beautiful as they are dangerous. Their red, cream, and black bands make lionfish a popular aquarium species to display, but you wouldn’t want to get too close to them because their sting is rather unpleasant and can cause severe nausea in humans.

Originally a native of the Indo-Pacific region, these visually stunning fish are a notoriously invasive species, and are currently thriving in the coastal waters of the Caribbean and the southeast USA. Their encroachment has wreaked havoc on the local ecosystem because they compete for food and have no natural predators in the area. Their invasion is further fuelled by the fact that native species do not recognise them as a predator, which makes it easy for lionfish to make a meal out of the local species.

See Some Scary Sea Predators for Yourself

If you’re feeling brave enough, come and see some of these scary sea predators at Blue Reef Aquarium Portsmouth. While you’re visiting, make the most of our daily talks and feeds, all included in the price of your ticket. Book your tickets in advance online to make the most of our seasonal discounts.

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