Sea butterflies

Sea angels are named after their resemblance to snow angels - they have translucent white bodies, with a wing-like structure on both sides of their body. Although they may look like snow angels, they are actually a large group of extremely small, swimming sea slugs!

Robin fish

One-millimeter mollusks could hold clues to the health of oceans

Inside the White Sea Biological Station is an unlikely photo studio where Alexander Semenov, 25, is sharing his stunning photographs of arctic sea creatures with the global online community.

Sea butterflies, also known as pteropods, are related to snails but they use their muscular foot to swim through the ocean rather than creep along the ground.

Sea angels (clade Gymnosomata) are a large group of extremely small, swimming sea slugs, not to be confused with Hydrozoans (Jellies and other similar creatures), classified into six different families. They are pelagic opisthobranchs in the clade Gymnosomata within the larger clade Heterobranchia.

The pulsing orbs and tentacled balls of flesh live 130ft underwater, encased under the ice sheets of the Russian Arctic, in temperatures only just above freezing.