Wonder how the Spanish dancer, or Hexabranchus sanguineus, got its common name? When it swims, the frilled edges of its mantle resemble the color and movement of the skirts of a flamenco dancer.
When they're not swimming, Spanish dancers crawl along relatively flat surfaces with the edges of their mantle tucked up close to their bodies (see the picture). They feed on sponges and can produce a toxic chemical to protect themselves from predation.
(One of the coolest things about Spanish dancers is that their gills are totally external -- see them? They are those whiter feathery things on the right side of the one pictured.)