This nocturnal sea urchin (Leptodiadema purpureum) is among the fastest sea urchins, retreating quickly from light. This one appears to have a small commensal shrimp living among its spines, although the precise species is unclear. The spines should be avoided, as they can cause intense pain.

This urchin was photographed in about 35 feet of water off the south Kohala Coast near the Mauna Lani Resort on the Big Island of Hawaii.