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

Pete Oxford / Upside down Jellyfish (Cassiopeia sp) Jardines de la Reina National Park, Cuba, Caribbean

Suzi Eszterhas / Two Purple / Striped Jellyfish (Pelegia / Chrysaora colorata) Monterey Bay Aquarium, California, USA, Captive

David Shale / Deepsea Medusa jellyfish (Colobonema sp), Mid-Atlantic Ridge, North Atlantic Ocean

Chris Newbert / Papuan Jellyfish (Mastigias papua) 20 feet deep, Solomon Islands

Chris Newbert / Papuan Jellyfish (Mastigias papua) 20 feet deep, Solomon Islands

Stephane Granzotto / Diver with Jellyfish (Rophilema nomadica) Mediterranean sea, Israel. Invasive species.

David Fleetham / Upsidedown jellyfish (Cassiopea medusae) resting in water, Komodo, Indonesia.

Claudio Contreras / Upsidedown Jelly (Cassiopea frondosa), Jardines de la Reina / Gardens of the Queen National Park, Caribbean Sea, Ciego de Avila, Cuba, January

Suzi Eszterhas / Comb Jelly (Leucothea pulchra), native to Pacific Ocean

Constantinos Petrinos / Jellyfish carry crab (Ethusa sp.) carrying Upside-down Jellyfish (Cassiopeia andromeda). Lembeh Strait, North Sulawesi, Indonesia.

Pete Oxford / Mangrove upsidedown jelly (Cassiopea xamachana) Lighthouse Reef Atoll, Belize.

Georgette Douwma / Upside down jellyfish (Cassiopeia andromeda) on sea bed with algae. Lembeh, Sulawesi, Indonesia.

Suzi Eszterhas / Purple-striped Jellyfish (Chrysaora colorata), California

Pete Oxford / Upside-down Jellyfish (Cassiopea xamachana), Lighthouse Reef, Belize

Pascal Kobeh / Upside-down jellyfish (Cassiopea andromeda), Maldives, Indian Ocean.

Hiroya Minakuchi / Upside-down Jellyfish (Cassiopea sp), Japan

Pascal Kobeh / Moon jellyfish (Aurelia labiata) close to the surface and under the sun rays, Alaska, USA, Gulf of Alaska. Pacific ocean.

Alex Mustard / Jellyfish carry crab (Ethusa sp) carrying an upside down jellyfish (Cassiopeia andromeda) at night. Komodo Island, Komodo National Park, Indonesia. Flores Sea.

Hiroya Minakuchi / Moon Jelly (Aurelia aurita) pair, Prince William Sound, Alaska

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens) group in an aquarium

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens) group in an aquarium

Pete Oxford / Upside down Jellyfish (Cassiopeia sp) Jardines de la Reina National Park, Cuba, Caribbean

Christian Ziegler / Upside-down Jellyfish (Cassiopea xamachana) floating between the aerial roots of Red Mangrove (Rhizophora mangle), Twin Cays, Carrie Bow Cay, Belize

Pete Oxford / Upside-down Jellyfish (Cassiopea xamachana), Bonaire, Netherlands Antilles, Caribbean

Juergen Freund / Decorator crab (Dorippe frascone) with an Upside down jellyfish (Cassiopea andromeda) on its back. The jellyfish is bigger than the crab! Palawan, Philippines.

Jurgen Freund / Carrier crab (Dorippe frascone) with an upside down jellyfish (Cassiopea andromeda) on its back. The jellyfish is bigger than the crab! Palawan, Philippines

Pete Oxford / Upside-down Jellyfish (Cassiopea sp), Jardines de la Reina National Park, Cuba

Pete Oxford / Upside-down Jellyfish (Cassiopea sp), Jardines de la Reina National Park, Cuba

Pete Oxford / Upside-down Jellyfish (Cassiopea sp), Jardines de la Reina National Park, Cuba

Pete Oxford / Upside-down Jellyfish (Cassiopea sp) pair on ocean floor, Jardines de la Reina National Park, Cuba

Georgette Douwma / Upside down jellyfish (Cassiopeia andromeda) on sea bed, Rinca, Komodo National Park, Indonesia, October

Juergen Freund / Specimens of Upside-down jellyfish {Cassiopeia sp} collected as part of the Coral Reef census, Lizard Island, Queensland, Australia, April 2008

Juergen Freund / Jo Browne removes with a pipet, mucous emitted by stressed Upside-down jellyfish specimens, part of the Coral Reef census, Lizard Island, Queensland, Australia, April 2008

Juergen Freund / Joanna Browne collecting an 'upside down jellyfish' {Cassiopeia sp} from the sandy bottom of Lizard Island lagoon, for Coral Reef census, Lizard Island, Queensland, Australia, April 2008

Tim Laman / Upsidedown Jellyfish {Cassiopeia sp} in a mangrove lagoon amongst the roots of Red Mangrove trees. Tunicate Cove, Belize. This jellyfish has symbiotic algae in its tentacles and stays upside-down to p...

Tim Laman / Upsidedown Jellyfish {Cassiopeia sp} in a mangrove lagoon amongst the roots of Red Mangrove trees. Tunicate Cove, Belize. This jellyfish has symbiotic algae in its tentacles and stays upside-down to p...

David Shale / Deep sea medusa {Solmissus sp} Gulf of Maine, Atlantic

Juergen Freund / Upside down jelly free swimming (Cassiopeia sp) Caribbean

Juergen Freund / Upside-down jellyfish {Cassiopeia sp} Kakaban Lake, Kalimantan, Indonesia

Juergen Freund / Upside-down jellyfish {Cassiopeia sp} caught by sea anemone, Indonesia, Kakaban

Juergen Freund / Upside-down jellyfish {Cassiopeia sp} about to be eaten by sea anemone, Indonesia,

Juergen Freund / Upside-down jellyfish {Cassiopeia sp} caught by sea anemone, Kakaban Lake, Kalimanta

Juergen Freund / Upside-down jellyfish {Cassiopeia sp} caught by sea anemone, Indonesia, Kakaban

Juergen Freund / Upside-down jellyfish {Cassiopeia sp} caught by sea anemone, Indonesia, Kakaban

Chris Newbert / Papuan Jellyfish (Mastigias papua) 20 feet deep, Solomon Islands

Chris Newbert / Papuan Jellyfish (Mastigias papua) 20 feet deep, Solomon Islands

Norbert Wu / Papuan Jellyfish (Mastigias papua) this species stings, relative to non-stinging species in lakes, Palau

Norbert Wu / Upside-down Jellyfish (Cassiopea xamachana) with symbiotic Algae (Zooxanthellae) in body, Caribbean

Norbert Wu / Papuan Jellyfish (Mastigias papua) has a powerful sting as opposed to their stingless cousins in landlocked Jellyfish Lake, Palau

Norbert Wu / Upside-down Jellyfish (Cassiopea xamachana) lies on bottom, symbiotic algae (Zooxanthellae) in body, Caribbean

Norbert Wu / Papuan Jellyfish (Mastigias papua) often lies upside-down on lagoon floor, South Pacific

Norbert Wu / Papuan Jellyfish (Mastigias papua) in rare landlocked lake, Kakaban Island, Borneo

Norbert Wu / Upside-down Jellyfish (Cassiopea xamachana) in rare landlocked lake, Kakaban Island, Borneo

Francis Abbott / Upside down jellyfish (Cassiopeia andromeda) Pacific, Yap, Palau.

Juergen Freund / Upside down jellyfish {Cassiopeia) Caribbean

Juergen Freund / Upsidedown jellyfish {Cassiopeia sp} + anemone in brackish water lake, Kalaban Is, Kalimantan, Indonesia. Anemones feed on jellyfish

David Fleetham / Brown jellyfish (Chrysaora melanaster), California, USA.

Suzi Eszterhas / Black Sea Nettle (Chrysaora achlyos), native to Pacific Ocean

Norbert Wu / Jack (Pseudocaranx sp) juveniles find shelter within stinging tentacles of jellyfish, South Australia, Australia

Christian Ziegler / Upside-down Jellyfish (Cassiopea xamachana), Bastimentos Marine National Park, Bocas del Toro, Panama

Pete Oxford / Upside-down Jellyfish (Cassiopea sp), Jardines de la Reina National Park, Cuba

Pete Oxford / Upside-down Jellyfish (Cassiopea sp), Jardines de la Reina National Park, Cuba

Pete Oxford / Upside-down Jellyfish (Cassiopea sp), Jardines de la Reina National Park, Cuba

David Hall / Upside down jellyfish {Cassiopeia frondosa} Dominica West Indies Symbiotic algae in

Lewis Jefferies / Grey seal (Halichoerus grypus) swimming downwards with Moon jellyfish (Aurelia aurita) in background, Lundy Island, Bristol Channel, Devon, UK.

Joel Sartore / Photo Ark / African upside-down jellyfish (Cassiopea depressa) moving 'bell', Oklahoma Aquarium. Captive.

Joel Sartore / Photo Ark / Two Inverted jellyfish (Cassiopea xamachana) underside portrait, Loro Parque's Aquarium, Tenerife. Captive.

David Fleetham / An Upside-down jellyfish (Cassiopea medusae) washed ashore at high tide and likely to die when the ocean recedes, Yap, Micronesia.

David Fleetham / Mangrove upsidedown jellyfish (Cassiopea xamachana), Florida, USA. This species mimics sea anemones by resting with its tentacles positioned on top when on the sea floor.

David Hall / Split level of a Lion's mane Jellyfish (Cyanea capillata) and Feather-boa kelp (Egregia menziesii), Seven-tree Island, Browning Pass, Queen Charlotte Strait, British Columbia, Canada. September.

Willem Kolvoort / Upside down jellyfish (Cassiopea sp) in a very muddy jellyfish pool that has underground connection with Aldabra lagoon, Picard Island, Aldabra, Indian Ocean

Willem Kolvoort / Jellyfish pool on Picard Island, home to Upside down jellyfish (Cassiopea sp). The water is very muddy but there is underground connection with the lagoon of Aldabra, Picard Island, Aldabra, Indian Oc...

Willem Kolvoort / Upside down jellyfish (Cassiopea sp) in a very muddy jellyfish pool that has underground connection with Aldabra lagoon, Picard Island, Aldabra, Indian Ocean

Willem Kolvoort / Upside down jellyfish (Cassiopea sp) in a very muddy jellyfish pool that has underground connection with Aldabra lagoon, Picard Island, Aldabra, Indian Ocean

Willem Kolvoort / Upside down jellyfish (Cassiopea sp) in a very muddy jellyfish pool that has underground connection with Aldabra lagoon, Picard Island, Aldabra, Indian Ocean

David Fleetham / Upsidedown jellyfish (Cassiopea medusae) is resting bell down, tentacles up, on sandy bottoms off Wakaya Island, Fiji.