The waters around Britain are home to a surprising variety of jellyfish – and these fascinating creatures, which have been drifting through the oceans for over 500 million years, are more common than many people realise – especially in the warmer months.
But which jellyfish species is the most common?
The commonest jellyfish in Britain
The moon jellyfish (Aurelia aurita) is the most commonly spotted jellyfish around the UK’s coastline.
Easily recognised by its translucent, saucer-shaped body and four distinct, purple rings visible through the top of its bell, the moon jelly is harmless to humans and often seen floating near the surface or washed up on beaches.
Growing up to 40cm in diameter, this gentle drifter uses its short tentacles to catch tiny plankton.
Moon jellies are often seen in bays, harbours and estuaries, particularly during summer when warm waters boost plankton growth and jellyfish numbers.
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Five more jellyfish seen in UK waters
Barrel jellyfish (Rhizostoma pulmo)
Sometimes called the 'dustbin lid jellyfish', the barrel jelly is one of the largest species found in British waters. It can grow to over 1 metre across and weigh up to 35kg. Despite its size, it poses little danger to humans, as its sting is mild. These jellies are most often seen in the south west and around Wales during spring and summer.
Blue jellyfish (Cyanea lamarckii)
This striking jellyfish is usually a vivid blue or purple colour, with a domed bell and long, flowing tentacles. Found mostly off western and northern coasts, it can give a sting, though it’s not considered dangerous.
Lion’s mane jellyfish (Cyanea capillata)
The lion’s mane is Britain’s largest stinging jellyfish, with long, trailing tentacles that can deliver a powerful sting. Found mostly in cooler northern waters, such as the North Sea and west coast of Scotland, it can grow up to 2 metres across.
Compass jellyfish (Chrysaora hysoscella)
This distinctive jellyfish is named for the dark brown, compass-like markings on its bell. Common along the southern and western coasts, it can sting, so it’s best admired from a safe distance.
Crystal jellyfish (Aequorea victoria)
This small, almost invisible jellyfish glows faintly in the dark due to bioluminescence. It’s occasionally spotted in rockpools or shallow waters but is harmless and beautiful.
Discover more wildlife found on the UK coast with our guides to rockpool species, whales and dolphins and seabirds.
Main image: moon jellyfish. Credit: Getty
