
21/08/2025
This is a sea urchin known as the Sea Potato Urchin (Astropyga radiata) or more commonly the Flower Urchin (though the exact species depends on region).
What you’re seeing is its vibrant test (outer shell) and the tube feet/spines that give it this alien-like look. The deep purple coloring and the almost "jelly-like" appendages are a defense adaptation and also help it move along rocks while clinging to surfaces in tidal zones.
It lives in shallow waters, often found clinging to rocks or coral, and plays an important role in the marine ecosystem by grazing on algae.