Everyone’s familiar enough with the great white shark. Carcharodon carcharias is, of course, the legendary predator from Steven Spielberg’s 1977 classic movie Jaws, a film which still has the power to make people decide never enter the ocean again. However, there are plenty of other plants and animals out there which could give you reason to think twice before leaving the safety of the beach – although in some instances even the beach isn’t safe, and you’d be better off at the hotel pool. Here are ten reasons why we definitely don’t like to be beside the seaside.

1. Eunice aphroditois –  the Bobbit worm

This loathsome toothed worm lurks in mud in the warm waters around Indonesia, northern Australia, and Sumatra. It matures when about 4 inches in length, but can grow up to almost 10 feet long. It eats almost anything, attacking at high velocity, sometimes with sufficient force to rip its prey in half. On top of that, it’s covered with spiny stingers which can cause permanent numbness in humans. One of these beauties obliterated an aquarium in the UK – it was only discovered when the owners, trying to find what was happening to their tropical fish, dismantled the artificial coral reef to find a 4-ft Bobbit worm nestling within. It is thought it had been in the reef since it was a juvenile, gradually growing to monster proportions using the unlimited source of food with which it was being provided.

2. Crocodylus porosus – saltwater crocodile

Native to coastal waters in south-east Asia, these giants regularly reach 5 meters (16 feet) in length – as long as a car. They are, essentially, up to 1000kg (2200lb) of pure muscle, which attack at great speed. They can take on, kill and eat large sharks, and even tigers have been attacked and killed by this most cunning and aggressive reptile. Humans are considered as fair game for these ferocious animals, and fatalities are reported most years. Saltwater crocodiles were responsible for a truly horrific series of attacks on humans on 19 February 1945. 400 embattled Japanese soldiers, marooned in a swamp and surrounded by enemy forces, were devoured by hundreds of the massive predators in a single night.

3. Astrotia stokesii – Stokes’ sea snake

Found in the Indian Ocean and the seas off Taiwan, this aggressive seagoing cousin of the cobra has fangs which are, distressingly, capable of biting through a wet suit. Sea snake venom is hugely toxic, although this particular species has not been responsible for human fatalities. Astrotia have been seen in vast numbers, with one report of a migrating column being six feet wide – and sixty miles long - probably not something to try to walk on.

4. Moorea producta – stinging limu / fireweed

The beautiful islands of Hawaii are home to this very unpleasant organism, which causes itching and burning of the skin for up to 48 hours. Worryingly, it appears to “target” (or, more accurately gets caught underneath) areas of skin covered by swim wear – often meaning sore, itchy rashes on the anus and genitals. The rash is caused by a bacterium (M. producta) which grows on the dark brown seagrass found in waters off the coast and which produces a cyanide-based toxin. In higher concentrations this poison is actually carcinogenic.

5. Synanceia verrucosa – stonefish

Responsible for producing what is one of the most staggeringly painful stings in the world, the stonefish lives quietly at the bottom of shallow, warm seas off the northern coast of Australia, just waiting to be stepped on. The effect of the venom has apparently caused victims to demand that their leg be amputated rather than suffer the appalling agony caused by the potent neurotoxin. As the stonefish can survive for up to a day out of water, it is entirely possible to be stung by one while walking on the beach. Better keep those sandals on!

6. Carcharhinus leucas – bull shark

Very aggressive and extremely protective of their own territories, bull sharks are found across the world, usually in warm tidal waters. Unusually, they can survive in freshwater as well as the sea and have even been known to attack horses and hippos in rivers. Although much smaller than their better known cousins, the great white, and almost completely blind, they are just as ready to attack a human – often by sizing a victim up with an initial bump with their heads. A bull shark who rubs up against you is not, therefore, giving you a playful hello, but is about to launch itself at you in a frenzy of razor-toothed fury.

7. Hapalochlaena lunulata – blue-ringed octopus

This small, rather beautiful octopus packs a particularly deadly punch. Although it has the decency to warn you when it is getting irritated (primarily by producing vivid blue rings on its otherwise brown skin) it can deliver a bite from its sharp central beak which contains a toxin some 10,000 times more deadly than cyanide. There is no antivenin for this, and a victim will typically become completely paralyzed - while remaining conscious and fully aware of what is happening to them. Only by keeping a person artificially ventilated is there any hope of surviving such a bite. The blue ringed octopus is found in the Pacific ocean and has been responsible for at least three known deaths.

8. Ulva – sea cabbage

The sea cabbage is a harmless form of algae which grows along the shoreline in Britain and France, where it usually does very little of note. However, with increasing global temperatures, the volumes of this plant have, in recent years, begun to increase dramatically. When the plants rot – and there can be thousands of tons of them on these coastlines – their decomposition produces extremely high levels of disgusting-smelling - and highly toxic - hydrogen sulfide gas. The stench of rotten eggs is bad enough, but the emissions have been sufficient to, quite literally, fell a horse (one died after stumbling into rotting seaweed in 2009.) Disturbingly, the problem is likely to become worse as climate change and pollution increase.

9. Conus geographus – geography cone

A beautiful shell found in many regions including the Red Sea and Indian Ocean, the geography cone is the most deadly shellfish known, responsible for over 30 deaths. The toxin it produces is similar to morphine and is fired out of the shellfish in a harpoon-like structure which is capable of puncturing wetsuits and rubber gloves. There is no known antidote to the venom, although with time, if a victim can be kept alive successfully, the body will metabolize it. As the cones are particularly attractive, they are often targeted by collectors despite the fact that they are capable of causing death within only a few hours, usually through respiratory failure.

10. Chironex fleckeri – the box jellyfish

The deadliest of all sea creatures, this sea jelly has a fearsome reputation. It lives off the coast of Australia, where it has killed over 80 people. It is almost invisible in the water and poses a major danger to swimmers, many of whom drown before reaching the shore after being stung by the the jellyfish’s 3 meter tentacles. The pain is utterly excruciating, with victims going very quickly into shock and possibly even experiencing cardiac arrest. Treatment is fortunately possible, with an antivenin being used alongside ordinary vinegar, which can be used to neutralize the toxin. It is thought that this simple treatment has, in fact, saved many lives over the past 100 years.