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

Hiroya Minakuchi / Jellyfish (Spirocodon saltator), Japan

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.

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.

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

Michael Pitts,Michael Pitts / Portuquese man o' war (Physalia physalis) colonial siphophore, Tobago, Caribbean.

Michele Westmorland / Snorkeler swimming with harmless Jellyfish (Mastigias papua etpisonii), Jellyfish Lake, Rock Islands, Palau, Micronesia.

Floris van Breugel / Tiny thimble jellyfish (Linuche unguiculata) drift with the current in the calm turquiose waters of a lagoon in Ofu, American Samoa. The window of sky is called Snell's Window, caused by refraction of...

Graham Eaton / Compass Jellyfish, in murky water, Abersoch, Cardigan Bay, Wales, July

Graham Eaton / Common / Moon Jellyfish (Aurelia aurita) seen from below. Cardigan Bay, Wales, June. Highly commended, marine category, British Wildlife Photography Awards (BWPA) competition 2012.