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

Alex Mustard / 2020VISION / Compass jellyfish (Chrysaora hysoscella) swimming over a rocky reef, Plymouth, Devon, UK, August. Did you know? Compass jellyfish change gender throughout their lives, starting off male, and later bec...

Suzi Eszterhas / Sea Nettle (Chrysaora quinquecirrha / achlyos) Monterey Bay Aquarium, California, USA, Captive

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

Neil Lucas / Sea nettles (Chrysaora quinquecirrha) in aquarium, with crowd of people watching, Atlanta, USA, October 2009

Richard Herrmann / Black Sea Nettle (Chrysaora achlyos), Coronado Islands, Baja California, Mexico

Richard Herrmann / Pacific Sea Nettle (Chrysaora fuscescens) group, Carmel, Monterey Bay, California

Graham Eaton / Compass Jellyfish (Chrysaora hysoscella) in clear water over seaweed Abersoch, Cardigan Bay, Wales, May

Richard Herrmann / Pacific Sea Nettle (Chrysaora fuscescens) group, Monterey Bay, Monterey, California

Richard Herrmann / Pacific Sea Nettle (Chrysaora fuscescens) group, Monterey Bay, Monterey, California

Richard Herrmann / Pacific Sea Nettle (Chrysaora fuscescens) group, Monterey Bay, Monterey, California

Graham Eaton / Compass Jellyfish (Chrysaora hysoscella) at sea surface. Abersoch, Wales, May.

Alex Mustard / Sea nettle jellyfish (Chrysaora quinquecirrha) with a small fish swimming alongside seeking shelter, West Palm Beach, Gulf Stream, Caribbean Sea, Florida, USA.

Suzi Eszterhas / Pacific Sea Nettle (Chrysaora fuscescens) group, California

Suzi Eszterhas / Pacific Sea Nettle (Chrysaora fuscescens) group, California

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

Neil Lucas / Portrait of a Sea nettle (Chrysaora quinquecirrha) in aquarium

Neil Lucas / Portrait of a Sea nettle (Chrysaora quinquecirrha) captive (aquarium)

Richard Herrmann / Black Sea Nettle (Chrysaora achlyos) photographed by diver, Coronado Islands, Baja California, Mexico

Richard Herrmann / Black Sea Nettle (Chrysaora achlyos), Coronado Islands, Baja California, Mexico

Richard Herrmann / Black Sea Nettle (Chrysaora achlyos), Coronado Islands, Baja California, Mexico

Richard Herrmann / Black Sea Nettle (Chrysaora achlyos), Coronado Islands, Baja California, Mexico

Richard Herrmann / Pacific Sea Nettle (Chrysaora fuscescens), Monterey Bay, California

Richard Herrmann / Pacific Sea Nettle (Chrysaora fuscescens) pair, Monterey Bay, California

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens) in aquarium, Japan

Philippe Clement / Compass jellyfish (Chrysaora hysoscella) stranded on beach, Brittany, France

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens), native to Pacific Ocean

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens) pair, native to the Pacific Ocean

Ingo Arndt / Pacific Sea Nettle (Chrysaora fuscescens) pair, California

Ingo Arndt / Pacific Sea Nettle (Chrysaora fuscescens) group watched by visitors at, California

Ingo Arndt / Pacific Sea Nettle (Chrysaora fuscescens), California

Ingo Arndt / Black Sea Nettle (Chrysaora achlyos), California

Ingo Arndt / Purple-striped Jellyfish (Chrysaora colorata), California

Hiroya Minakuchi / Purple-striped Jellyfish (Chrysaora colorata), native to coast of California

Hiroya Minakuchi / Purple-striped Jellyfish (Chrysaora colorata), native to coast of California

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens), native to Pacific Ocean

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens), native to Pacific Ocean

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens), native to Pacific Ocean

Hiroya Minakuchi / Purple-striped Jellyfish (Chrysaora colorata), native to coast of California

Kevin Schafer / Pacific Sea Nettle (Chrysaora fuscescens) group, Vancouver Aquarium, Vancouver, British Columbia, Canada

Kevin Schafer / Pacific Sea Nettle (Chrysaora fuscescens), Oregon Coast Aquarium, Oregon

Kevin Schafer / Pacific Sea Nettle (Chrysaora fuscescens), Oregon Coast Aquarium, Oregon

Kevin Schafer / Pacific Sea Nettle (Chrysaora fuscescens), California

Jeff Rotman / Sea Nettle Jellyfish (Chrysaora quinquecirrha) in open ocean, North Atlantic Ocean, USA

Michael Pitts / Compass jellyfish {Chrysaora hyoscella} with predated fish amongst tentacles, Isles of Scilly, UK

Hiroya Minakuchi / Black Sea Nettle (Chrysaora achlyos) spreading tentacles, aquarium, Japan

Hiroya Minakuchi / Pacific Sea Nettle (Chrysaora fuscescens) spreading tentacles, aquarium, Japan

Jose B. Ruiz / Compass Jellyfish {Chrysaora hyoscella} on Cala Fustera Beach, Benissa, Alicante, Spain.

Jose B. Ruiz / Compass Jellyfish {Chrysaora hyoscella} on Cala Fustera Beach, Benissa, Alicante, Spain.

Michael Pitts / Compass jellyfish {Chrysaora hyoscella} Isles of Scilly, Cornwall, UK.

Michael Durham / Sea Nettle (Chrysaora quinquecirrha) common species in Caribbean, US Atlantic Ocean and Gulf of Mexico

Michael Durham / Sea Nettle (Chrysaora quinquecirrha) common species in Caribbean, US Atlantic Ocean and Gulf of Mexico

Michael Durham / Sea Nettle (Chrysaora quinquecirrha) common species in Caribbean, US Atlantic Ocean and Gulf of Mexico

Michael Durham / Sea Nettle (Chrysaora quinquecirrha) with unidentified parasitic Crab, common species in Caribbean, US Atlantic Ocean and Gulf of Mexico

Hiroya Minakuchi / Northern Sea Nettle (Chrysaora melanaster), northern Pacific Ocean

Norbert Wu / Northern Sea Nettle (Chrysaora melanaster) gather in great number off Pacific coast in fall, Monterey, California

Norbert Wu / Northern Sea Nettle (Chrysaora melanaster) and scuba diver, southern California

Norbert Wu / Northern Sea Nettle (Chrysaora melanaster) and scuba diver, southern California

Tim Edwards / Compass jellyfish stranded on beach {Chrysaora hysoscella} Derrynane bay, Kerry, Republic of Ireland.

Martin Camm / Carwardine / Illustration of Compass Jellyfish (Chrysaora hysoscella), Cyaneidae; British jellyfish (Wildlife Art Company).

Sue Daly / Compass jellyfish {Chrysaora hyoscella} Jersey, Channel Isles

Tim Edwards / Compass jellyfish stranded on beach {Chrysaora hyoscella} Kerry, Republic of Ireland