Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 16 families within the order; they are thought to have a cosmopolitan distribution in tropical and temperate waters worldwide.
This is not a specially designed birthday cake. It is not a palette too – it is called Clown Nudibranch. This bright and uniquely colored sea slug can be found in the intertidal zones of temperate southern Australia and northern New Zealand.