Pair of sea angels (Clione limacina) mating. Sea angels are free-swimming sea slugs that inhabit the cold northern oceans of the world. They are simultaneous hermaphrodites, possessing both male and female sexual organs. They breed during spring and summer, each adult passing sperm to the other during this dance-like mating motion, after which both will lay eggs. Filmed off Novaya Zemlya, in the Russian Arctic Ocean.