Jellyfish in UK Waters: Which ones to watch out for and how to treat their stings.

The United Kingdom has a large variety of jellyfish species, some of which are harmless to us while others can inflict painful stings. We delve into the fascinating world of UK jellyfish and help you to identify the ones that you may need to look out for while you are swimming in the sea and what to do if you are stung by one.

UK jellyfish identification

1. Compass Jellyfish 

During summer months in UK waters, it is common to find the Compass Jellyfish, which is a native species. They have slim, elongated tentacles that can sting swimmers who are not aware. Though their sting is usually less severe than that of some other stinging species, some people may experience a stronger reaction.

2. Moon Jellyfish 

The most common jellyfish in UK waters, the Moon jellyfish can reach a size of up to 40cm in diameter. They are easily identified by their transparent, umbrella-shaped bell that is surrounded by short hair-like tentacles. The bell also contains four distinct pale purple rings. You are unlikely to be stung by a Moon jellyfish because their stinging cells are not strong enough to penetrate human skin.

 3. Barrel Jellyfish 

Did you know that barrel jellyfish can grow up to a meter in diameter? Otherwise known as Dustbin Lid Jellyfish, they have a round, solid bell that is rubbery in texture and can be white, pale pink, blue, or yellow. The bell is surrounded by purple markings. Although they don't have tentacles, they have eight thick, frilly arms that hang from the manubrium, which is located in the center of the bell's underside. A barrel jellyfish sting is not normally harmful to humans.

4. Lion's Mane Jellyfish 

The Lion's Mane Jellyfish is a popular and sizable jellyfish species found in the UK. These jellyfish can grow to be over one meter in diameter and have lengthy, flowing tentacles that resemble a lion's mane. Their tentacles are equipped with cells that may cause a painful sting to humans, even some time after being washed up on the beach. 

5. Mauve Stinger

The beautiful purple colour Mauve Stinger jellyfish has tentacles contain stinging cells. As the name suggests, the Mauve Stinger can give a painful sting to humans who come into contact with it. 

 6. Blue Jellyfish

Blue jellyfish can grow up to 30cm in size. Their shape is similar to the lion's mane jellyfish, however they are smaller with a distinct blue bell and visible radial lines. You may also find a yellow colour variety of this jellyfish in UK waters. These jellyfish can give you a mild sting.


Not jellyfish but worth a mention

Portuguese Man o'War and By-the-Wind Sailor

Portuguese Man o' War

The Portuguese Man o' War has a similar appearance to a jellyfish, although it's actually a floating colony of hydrozoans that typically float on the water's surface. These creatures have long tentacle-like polyps that contain venomous cells that can cause severe pain and inflammation if you touch them.

By the Wind Sailor

These hydrozoans are part of the same family as the Portuguese man o' war, but they are not as harmful. They can be easily recognized by their sail-shaped structure and blue hue. They are frequently found on beaches following storms.




How to treat a jellyfish sting

The good news is, the myth of weeing on a jellyfish sting is not recommended. If you happen to get stung by a jellyfish, it's important to act quickly as follows.

- rinse the affected area with seawater (not fresh water)
- remove any spines from the skin using tweezers or the edge of a bank card
- soak the area in very warm water (as hot as can be tolerated) for at least 30 minutes – use hot flannels or towels if you cannot soak it
- take painkillers if required
- if the sting is severe or if you experience symptoms such as difficulty breathing or chest pain, seek medical attention immediately.

Further information can be found from the NHS


The Marine Conservation Society provides further information about jellyfish found in UK waters