At only 4-7cm in size, this tiny, graceful swimmer is a sea slug with a gelatinous, translucent body. Commonly found in depths of over 500m in the Arctic, it flaps its adapted foot ‘wings’ to glide through the ocean. It may look cute, but it is a ferocious predator of its close relative, the sea butterfly. When feeding, the top of its head opens up and devil-like tentacles roll out, with which it devours its victim in under 2 minutes.