Glaucus atlanticus (common names include the sea swallow, blue angel, blue glaucus, blue dragon, blue sea slug and blue ocean slug) is a species of small, blue sea slug, a pelagic aeolid nudibranch, a shell-less gastropod mollusk in the family Glaucidae.
These sea slugs are pelagic: they float upside down by using the surface tension of the water to stay up, where they are carried along by the winds and ocean currents. They feed on on other pelagic creatures. This sea slug stores stinging nematocysts from the cnidarian within its own tissues as defense against predation. Humans handling the slug may receive a very painful and potentially dangerous sting.
