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JELLYFISH ON UK SHORES

Look, but
do not touch.

Most UK jellyfish are harmless to look at.

A translucent moon jellyfish with four pale purple rings drifting in clear green coastal water, lit by sunlight from above — AI-generated image, not a photograph of a real person or place.

A few have a sting worth respecting, and even a dead one on the sand can still sting. Here is how to tell them apart, and what the NHS says to do if one catches you.

SEA WATERnever fresh

Check a jellyfish

Keep in mind

Know the stingers
Rinse with seawater
Then warm water
A calmer day at the beach

THE SHORT ANSWER

A few sting hard,
most barely at all.

The Marine Conservation Society lists eight species seen around the UK.
Three need real care.

MILD

Moon and barrel

The moon jellyfish, with its four purple rings, and the big barrel jellyfish both have a mild sting, says the Marine Conservation Society.

Check a species

TAKE CARE

Lion's mane and friends

The lion's mane, mauve stinger and Portuguese man o' war come with a be very careful warning. The compass jellyfish stings too.

See the numbers

IF STUNG

Seawater, then warmth

The NHS says rinse with seawater, not fresh water, then soak in very warm water for at least 30 minutes. Do not pee on it.

What to do

A QUICK SPECIES CHECK

What have you
spotted?

Pick a jellyfish to see how the Marine Conservation Society describes its sting. The bar shows how much care it calls for.

Jellyfish check

Choose a speciesMoon jellyfishBarrel jellyfishCompass jellyfishLion's manePortuguese man o' war

Moon jellyfishMild sting

Up to 40 cm across, see-through, with four pale purple rings. The most common jellyfish in UK seas, says The Wildlife Trusts.

Barrel jellyfishMild sting

A solid, rubbery bell up to 1 m across with eight thick frilled arms and no tentacles. Often on beaches in May and June.

Compass jellyfishIt stings

A pale bell up to about 30 cm with brown V-shaped markings and 24 long, thin tentacles. Often washed ashore in summer.

Lion's maneBe very careful

A reddish-brown bell usually about 50 cm across, up to 2 m, with many long hair-like tentacles. Give it a wide berth.

Portuguese man o' warBe very careful

Not a true jellyfish but a floating colony with a blue-purple crest. Its tentacles may be tens of metres long and its sting is powerful.

Source: Marine Conservation Society, How to identify types of jellyfish in the UK; The Wildlife Trusts, Identify UK jellyfish.

Based on the Marine Conservation Society's UK jellyfish identification guide. This is general information, not medical advice.

TWO NUMBERS WORTH KNOWING

Beachgoers are
the jellyfish counters.

UK jellyfish records come largely from people on the beach.
Here is what they have added up to.

5,000+

Sightings of eight species, 2003 to 2011

A University of Exeter and Marine Conservation Society study drew on over 5,000 sightings reported by more than 3,500 beachgoers, the first UK-wide update in over 40 years.

SIGHTINGS · UNIVERSITY OF EXETER

1,133 reports

Jellyfish reports in a single year

2013 was a record year for the survey. By mid-July 2014 over 500 more reports were in, most of them barrel jellyfish from South West England and Wales.

RECORD YEAR · 2013

Why the 2014 barrel surge happened is uncertain. One researcher suggested a very mild winter may have let more adults survive at depth and rise as the water warmed.

WHAT THE NHS SAYS

Stung? Rinse,
then warm it.

These steps follow NHS guidance on jellyfish and other sea creature stings. Get local help from a lifeguard or first aider as soon as you can.

A hand holding a bowl of warm water and a folded towel on a beach blanket beside a first aid kit — AI-generated image, not a photograph of a real person or place.

Step 1

Rinse with seawater

Use seawater, not fresh water, and do not touch tentacles with bare hands. Lift off any bits with tweezers or the edge of a bank card.

Step 2

Soak in very warm water

As hot as can be tolerated, for at least 30 minutes. If you cannot soak it, use hot flannels or towels.

Step 3

Skip the myths

Do not pee on the sting, do not use ice or a cold pack, and do not cover or close the wound.

Step 4

Know when to call 999

Difficulty breathing, chest pain, fits, severe swelling, vomiting or fainting mean A&E or 999. A sting on the mouth, throat or near the eyes needs a minor injuries unit.

WHY BLOOMS HAPPEN

When the sea
fills with jellies.

A large barrel jellyfish with a pale rubbery bell washed up on wet sand at low tide, with the sea behind — AI-generated image, not a photograph of a real person or place.

A bloom is a sudden rise in jellyfish numbers. The Marine Conservation Society says blooms of most UK species typically appear in spring and last through autumn.

A 2009 review in Trends in Ecology and Evolution, led from the University of Queensland, linked bigger blooms to overfishing, which removes fish that keep jellyfish in check, and to excess nutrients from fertilisers and sewage, with warmer seas a possible further factor.

Questions

Questions on the way

Can a dead jellyfish on the beach still sting?

Yes. The Marine Conservation Society advises against touching jellyfish even when they have washed up, because a dead jellyfish can still sting.

Should I pee on a jellyfish sting?

No. NHS guidance says do not pee on the sting. Rinse it with seawater instead, then soak it in very warm water for at least 30 minutes.

Why not rinse with fresh water?

The NHS advice is specific: rinse the area with seawater, not fresh water, and do not touch any tentacles with your bare hands.

Which UK jellyfish is the most dangerous?

The Marine Conservation Society gives its strongest warnings to the lion's mane, the mauve stinger and the Portuguese man o' war, which it calls extremely dangerous to humans.

When do I need urgent help after a sting?

The NHS says go to A&E or call 999 for difficulty breathing, chest pain, fits, severe swelling or bleeding, vomiting, lightheadedness or loss of consciousness.

Destination

Where the facts come from

Updated 14 October 2026

Look, butdo not touch.

A few sting hard,most barely at all.