Wales Beach Guide

A Quick Guide to Jellyfish

Jellyfish are commonly seen washed up on the beaches during the summer months, but fortunately in Wales, most are relatively harmless and stings can be easily treated. The sting is caused by specialized cells called nematocysts, which are triggered by contact, and inject venom into the victim. If stung, the current advice is to remove any remaining stinging cells with tweezers, or gently scrape the affected area with a straight edge (e.g. a credit card). It is now thought that the old treatment of applying vinegar (even if you had some) is ineffective. Jellyfish typically have a lifespan of just a few months, and are made up of around 90% water.
Moon Jellyfish

Moon Jellyfish

These are the most common jellyfish around the coasts of Wales, and have only a mild sting. They can be identified by the four pink or purple rings. They can reach up to a foot in diameter.
Barrel Jellyfish

Barrel Jellyfish

These can be up to 3 feet across, and occasionally are washed up on the shore in their thousands. They only have a very mild sting, and (unless you're squeamish about touching them) are no reason to avoid going into the sea.
Blue Jellyfish

Blue Jellyfish

These can reach up to 6 inches across and have a mild sting.
By-the-wind Sailor

By-the-wind Sailor

These have an oval deep blue body about 2 to 3 inches wide, with a vertical triangular vane on top. They are not true jellyfish, and are harmless. Frequently washed ashore in their thousands.
Lions Mane

Lion's Mane Jellyfish

This is a stinging species and easily identified by its orange or rust-brown colour. It can reach up to 18 inches wide, and is more common in North rather than South Wales.
Compass Jellyfish

Compass Jellyfish

This is a stinging species, and can grow up to a foot in diameter. Easily identified by its brown V-shaped markings.