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

Georgette Douwma / Upside down jellyfish (Cassiopeia andromeda) Lembeh, Sulawesi, Indonesia.

Franco Banfi / Freshwater jellyfish (Craspedacusta sowerbii) Lake Lugano, Ticino, Switzerland. August. Invasive species.

Franco Banfi / Freshwater jellyfish (Craspedacusta sowerbii) Lake Lugano, Ticino, Switzerland. August. Invasive species.

Jordi Chias / Atolla jellyfish (Atolla wyvillei) with Gentoo penguin (Pygoscelis papua) in the background near the surface. Antarctic Peninsula. Finalist in the Underwater category of the Wildlife Photographer of t...

Juergen Freund / Split level of large Purple crown jellyfish (Netrostoma setouchina) in shallows of mangroves. Mali Island, Macuata Province, Fiji, South Pacific.

Barry Bland / Fried egg jelly fish (Cotylorhiza tuberculata) Mediterranean Sea.

Aflo / Northern sea nettle (Chrysaora Melanaster) floating, with Mackerel fry ( Carangidae) Izu, Japan. January.

Pascal Kobeh / Multitudes of Moon jellyfish (Aurelia labiata), Alaska, USA, Gulf of Alaska. Pacific ocean.

Claudio Contreras,Claudio Contreras / Jellyfish, Inanuran Island, Danajon Bank, Central Visayas, Philippines, April

Wild Wonders of Europe / Lundgren / True jelly fish (Pelagia noctiluca) Pico, Azores, Portugal, June 2009

Wild Wonders of Europe / Lundgren / True jelly fish (Pelagia noctiluca) Pico, Azores, Portugal, June 2009