Spanish dancer

noun2

1. •
   A species of nudibranch sea slug, Hexabranchus sanguineus, commonly growing up to a length of 25 centimetres (about 9.8 inches), with some in the Red Sea up to 40 centimetres (15.7 inches).
2. •
   A species of deep-sea sea cucumber, Enypniastes eximia, with webbed swimming fin-like structures at the front and back of its body.