Sue Daly / Barrel jellyfish (Rhizostoma octopus) swimming past, Sark, British Channel Islands, UK, September.

Stephane Granzotto / Jellyfish (Rhizostoma pulmo) Mediterranean sea, Corsica

Stephane Granzotto / Jellyfish (Rhizostoma pulmo) Mediterranean sea, Corsica

Stephane Granzotto / Jellyfish (Rhizostoma pulmo) Mediterranean sea, Corsica

Stephane Granzotto / Jellyfish (Rhizostoma pulmo) Mediterranean sea, Corsica

Stephane Granzotto / Jellyfish (Rhizostoma pulmo) Mediterranean sea, Corsica

Graham Eaton / Rhisostome / Barrel jellyfish (Rhizostoma octopus) stranded on a sandy beach, Abersoch, Gwynedd, Cardigan Bay, Wales, April.

Philippe Clement / Barrel jellyfish (Rhizostoma octopus) washed up on beach along the North Sea coast, Nord-Pas-de-Calais, France, August

Jeff Rotman / Barrel jellyfish {Rhizostoma octopus} indicating plankton migration, Irish sea.

Jeff Rotman / Barrel jellyfish {Rhizostoma octopus} indicates plankton migration, Irish Sea, UK

Bernard Castelein / Barrel jellyfish stranded on beach {Rhizostoma octopus} Texel, The Netherlands

Sue Daly / Barrel jellyfish {Rhizostoma octopus} Jersey, Channel Isles, UK