Which jellyfish will give swimmers a sting?

With more jellyfish reported appearing around UK coasts, how do you tell which species they are and which ones have the nastiest sting?

If you are taking a dip, you might encounter barrel, moon, blue, compass and mauve stinger jellyfish.

Devon Wildlife Trust expert Carli Cocciardi explained how to tell them apart, and why the Portuguese man o' war is definitely worth watching out for.