Juergen Freund / Mermaid's wineglass algae (Acetabularia calyculus) Batangas, Philippines.

Alex Mustard / The Guardian Of The Reef Statue, with diver, Lighthouse Point. Grand Cayman, Cayman Islands, Caribbean Sea.

Solvin Zankl / Mermaid's wine glass / green algae (Acetabularia acetabulum) San Pietro Island, Sardinia, Italy, Mediterranean, July

Philippe Clement / Egg case / mermaids purse of a Thornback ray / skate (Raja clavata) on beach, Normandy, France

Philippe Clement / Egg case / Mermaids purse of a Thornback ray / skate (Raja clavata), Normandy, France

Elizabeth White / Egg cases / mermaids purse of deepsea ray {Bathyraja richardsoni} North Atlantic

Jose B. Ruiz / Mermaid's wineglass seaweed {Acetabularia acetabulum} Mediterranean

Jose B. Ruiz / Mermaid's wineglass seaweed {Acetabularia acetabulum} Mediterranean

Nature Production / Egg case of Blotchy swell shark {Cephaloscyllium umbratile} attached to coral, Izu, Shizuoka, Tokyo, Japan

Geoff Simpson / Eggcase (mermaid's purse) of Larger spotter dogfish {Scyliorhinus stellaris} Wales

Shane Gross / Caribbean reef octopus (Octopus briareus) moving over Mermaid's wine glass (Acetabularia acetabulum) on seabed, hunting at night, Seahorse National Park, Bahamas, Caribbean Sea.

Shane Gross / Lined seahorse (Hippocampus erectus) among Mermaid's wine glass (Acetabularia acetabulum) at night, Seahorse National Park, Bahamas, Caribbean Sea.