Land slugs and snails are dull affairs that leave little to be desired, but if you've ever been deep sea diving you will know that the ocean’s versions are much more vibrant. Hidden beneath the sea are hundreds and thousands of colorful slugs, in bright hues that would make you think they’re from another planet. Many of these colorful creatures used to be snails that shed their shells and evolved into sublime sea slugs.
Cuthona sibogae
Lettuce sea slug (Elysia crispata)
Nembrotha kubaryana
Okenia hopkinsia rosacea
Donut nudibranch (Doto greenamyeri) 
Hydatina physis
Phyllidiella pustulosa
Cadlinella ornatissima
Sea sheep (Costasiella kuroshimae) 
Hypselodoris kanga
Janolus fuscus
Hypselodoris festiva
Chromodoris strigata
Phyllodesmium serratum
Sacoglossan sea slug (Cyerce nigrican) 
Glossodoris atromarginata
Hermissenda crassicornis
Dirona albolineata
Chromodoris reticulata
Blue angel (Glaucus atlanticus)
Phyllodesmium poindimiei
h/t: boredpanda
