Alex Mustard,Alex Mustard / A nudibranch (Dendronotus frondosus) photographed in the field aquarium, Gulen, Norway. North East Atlantic.

Alex Mustard,Alex Mustard / A portrait of a nudibranch ( Limacia clavigera) searching for food on algae. Gulen, Norway. North East Atlantic Ocean.

Alex Mustard / 2020VISION / Nudibranch eggs (Tritonia hombergi) Loch Carron, Ross and Cromarty, Scotland, UK, April

Juergen Freund / Chromodoris nudibranch (Cadlinella sp.) Lembeh Strait, North Sulawesi, Indonesia.

Birgitte Wilms / Nudibranch laying eggs, Indonesia

Norbert Wu / Flamingo Tongue Snail (Cyphoma gibbosum) feeding on Common Sea Fan (Gorgonia ventalina) showing deep purple tone where the Sea Fan has released protective compounds, Saba, Caribbean

Fred Bavendam / Cowry living on Sea Fan (Solenocaulon sp), Bali, Indonesia

Norbert Wu / Cone Snail (Conus dalli), Sea of Cortez, Baja California, Mexico

Flip Nicklin / Naked Sea Butterfly (Clione limacina) underwater portrait, Arctic

Franco Banfi / Headshield slugs (Micromelo undatus) Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean

Ingo Arndt / Cone Top Shell (Tectus conus) from Indo-Pacific, Meeresmuseum Ozeania, Riedenburg, Germany

Franco Banfi / Sap sucking seaslug (Plakobranchus ocellatus) Blue water mangrove, Raja Ampat, Irian Jaya, West Papua, Indonesia, Pacific Ocean