The Glaucus atlanticus, or blue glaucus is one of only two species in the family Glaucidae. Also known as the blue dragon, this creature is a is a species of blue sea slug.
The animals float upside down at the surface of the sea, keeping afloat by swallowing air which is stored in their stomachs.
Their diet is mainly made up of hydrozoans including the Portuguese Man o’ War - they even eat the stings. As well as getting nourishment from the stings, they use them for their own defence.