Blue Sea Slug are also known as the sea swallow, blue angel, blue glaucus, blue dragon and blue ocean slug. The Glaucus atlanticus is a small species. These sea slugs are pelagic and it can be found in the Indian Ocean and Pacific Ocean.
Glaucus atlanticus is camouflaged. The blue side of their body faces upwards, blending in with the blue of the water. The silver/grey side of the sea slugs faces downwards, blending in with the silvery surface of the sea. It can be up to 3 cm in length. It is silvery grey on its dorsal side and dark and pale blue ventrally. It has dark blue stripes on its head. In this species the cerata (saw teeth on the skin) are arranged in a single row in each arch.
Although these sea slugs live on the open ocean. They sometimes accidentally wash up onto the shore and therefore they may be found on beaches. When humans are stung by Glaucus atlanticus, the venom stored in the nematocysts is injected under the skin. This venom has been shown to cause fever, shock and problems with the heart and lungs. In very rare cases this venom has even led to death.