What are jellyfish, and what should you do if you come across one while swimming on holiday?

What are jellyfish?

Mushroom shaped, generally translucent sea creatures that bob along in the water – known as ‘free-swimming’ – with tentacles that can be covered in poisonous sacs called nematocysts.

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Types of jellyfish you might see on a British beach

According to The Marine Biological Association, there are more than two hundred species of true jellyfish globally, but only six species are commonly found in British waters.

They are:

1. Moon jellyfish (Aurelia aurita) – it has four white rings you can see through its umbrella.
2. Compass jellyfish (Chrysaora hysoscella) – has dark ‘compass’ markings on its umbrella.
3. Lion’s mane jellyfish (Cyanea capillata) – the second longest recorded animal in the world (it can grow up to 30m), it has red and orange tentacles in bunches.
4. Dustbin-lid jellyfish (Rhizostoma pulmo) – this can grow up to 90 cm across
5. Blue jellyfish (Cyanea lamarckii) – as its name suggests, this guy is bright blue.
6. Mauve stinger (Pelagia noctiluca) – these sting and are capable of bioluminescence (creating its own light).

What to do in the water if there are jellyfish

Jellyfish – although some can provide their own momentum – are generally at the mercy of the current, hence why they often get washed up. Being vigilant, especially in warm shallow waters which they love, is your best bet for avoiding a nasty sting.

If you do spot a jellyfish floating along, don’t try and move it or wave it away, just move out of its path and stick your hand in the air to alert others to its presence. If there are large numbers that are hard to avoid, don’t risk it, get out and, if the beach you’re on has a lifeguard, let them know. Often lifeguards put up flags if there’s a significant jellyfish population nearby. Alternatively, wear a full body wetsuit or protective waterproof footwear.

What to do on land

Look out for flags announcing whether large numbers of jellyfish have been spotted, even if there isn’t a flag, watch your feet in the shallows and along the tide line.

This is where jellyfish tend to congregate and get stranded on the sand. While many don’t sting, some do, and they can be unpleasantly slimy to step on anyway! If you’re taking the dog for a walk, best to stop them nibbling or rolling in dead jellyfish too.

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What to do if you get stung by a jellyfish

If you do get stung, get out of the water immediately and have someone remove any attached tentacles with a pair of tweezers.

Apply a heat pad or run the site under hot water – it’ll help with the pain. Anti-histamines can help relieve swelling, while paracetamol can help with any residual pain. Seek medical advice if you have a severe allergic reaction, or become short of breath.

And don’t listen to anyone who says the sting needs to be weed on – it’s not true!

What do you do when you spot a jellyfish on the beach? Tell us in the comments below