The English Channel isn’t known for its dangerous marine life but there are some animals that can cause painful injuries.
Thankfully, British waters don’t tend to have as many dangerous or venomous creatures as the tropical seas in the Indo-Pacific or the shark-filled waters of Florida or Australia. But we do have some potentially dangerous animals that can harm humans (very often unintentionally).
Here’s our pick of some of the potentially dangerous marine life found in the English Channel.
Weever fish
Generally, UK waters aren’t a haven for venomous fish but we do have some. Possibly the most famous is the lesser weever fish (Echiichthys vipera), which you might have heard of – or even stepped on yourself.
These small fish are almost impossible to see when they bury themselves in the sand so barefoot beachgoers often step on them, getting stung by their venomous dorsal spines in the process. You’re most likely to get on the wrong side of a weever fish during summer while out walking at low tide on a sunny day. To prevent getting stung by these 15cm fish, wear beach shoes.
If you think you’ve been stung (your foot will hurt and may swell or go numb), find your nearest RNLI lifeguard who is trained to provide medical care in these situations. Fatalities from weever fish stings are exceptionally rare.
Common stingray
Common stingrays are a particular threat to anglers in the English Channel who can get stung while handling these venomous animals after catching them. Attacking a human isn’t the stingray’s go-to – they only do this when they feel they have no other way of escaping the potential threat (like swimming away). Mostly, they tend to be very timid animals.
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But if you surprise, corner or step on them and they decide to deploy their sting, it can be nasty. Their sharp tail barb punctures your skin and the ray injects a toxic venom. It’s as painful as it sounds and you’re likely going to need to get to a doctor as soon as possible.
It’s very unlikely that a sting would kill you – under 20 people around the world have reportedly been killed by stingrays in the last 80 years – but avoid putting yourself in danger by shuffling in shallow waters without picking up your feet (so you don’t unintentionally step on a hidden ray) and minimise any handling of the animal if you catch one while fishing.
Bottlenose dolphins
People often underestimate the size and power of bottlenose dolphins. In UK waters, these animals can grow much larger and heavier than others around the world, sometimes measuring up to four metres long and tipping the scales at up to 500 kilograms. To put that in perspective, an adult female polar bear usually weighs less than 300kg.
And any animal this large – and made of muscle – can potentially harm humans.
In 2025, a solitary bottlenose dolphin called Reggie hit the headlines when he started getting overly friendly with tourists in Dorset. Reggie is said to have pushed swimmers underwater, causing experts to warn people to keep away and reminding them that Reggie was probably stressed out from being disturbed by so many tourists.
Reggie wasn’t trying to hurt anyone on purpose but some people were left shaken up by their encounter, and they could have been badly injured. As with any wild animal, it’s important to give dolphins plenty of space – for your own safety, and theirs.
Grey seals
Seals might look a bit like cute puppies but, like dogs, you don’t want to get bitten by one.
It’s normal to see a seal on the beach because these animals come on land to rest so, usually, they just need their space. Try to stay at least 100 metres away and keep dogs on leads (and children close to you) when you see a seal on the coastline so that you don’t disturb them.
When seals feel threatened, they do what many animals do: try to defend themselves. This means these large animals (adult grey seals can weigh as much as 300kg) can sometimes bite humans who try to approach them. Their teeth are teeming with bacteria so a bite will land you in hospital as you’ll need to get a course of medication to prevent any infections.
Lion’s mane jellyfish
One of the world’s largest species of jellyfish swims through the English Channel and its stings can be seriously painful. The Lion’s mane jelly got its name from its bushy red tentacles, which look like – you guessed it – a lion’s mane.
These large jellyfish have tentacles that can trail through the water for several metres and if you come into contact with them, it’s going to hurt. Stings are not usually fatal but the pain, welts, swelling and nausea will probably ruin your summer swim.
If you do get stung, contact a medical professional for treatment.
Basking shark
Bus-sized basking sharks cruise through UK waters in the summer. Although they’re most commonly seen off the coasts of Cornwall, Ireland and Scotland, they may swim through the western English Channel as part of their journey.
Although most of the 500+ species of shark are harmless to humans, these titans are the epitome of gentle giants. Despite their size, the second largest shark in the world feeds on tiny plankton. You can even go snorkelling with them.
But, as with any large, wild animal, colliding with a human is going to do some damage – and that’s proven to be true for basking sharks. In 1937, one of these huge sharks breached out of the water and landed on a boat, causing three of the five people onboard to drown.
If you’re in British waters, there’s no need to worry about the same happening to you. This tragic event is the only fatality by a basking shark on record. That said, giving them plenty of space is always a good idea and improves the encounter too, as there’s less chance of scaring them away.
Portuguese man o' war
The name of the Portuguese man o' war might be your first clue that these colonial animals aren’t messing around. Although they don’t target people (they can’t control the direction they swim in, instead just drifting with the current), if you accidentally touch one of their venomous tentacles, you could experience pain, swelling and even vomiting.
A sting is not typically fatal but it’s definitely not pleasant. So, if you see one of these blue jellyfish-like creatures (they're actually a siphonophore) in the waters of the English Channel or washed up on the coastline, avoid touching them. You can even be stung by a dead one!
