Antipatharians are tree-like or stick-like cnidarians with a solid dark brown skeleton decorated with small spines or knobs.  The rough surface distinguishes it from gorgonians and arborescent hydroids, which are nearly absent in shallow Hawaiian waters.   Colonies occur along current-swept drop-offs and under ledges.  Live colonies may be  rusty brown, orange, yellow, green, or white due to color of the polyps.  They may also fluoresce; this color is not recorded when a flash photograph is taken.  Antipatharians provide food or shelter to several forms of marine life, including fishes, mollusks, and crustaceans.    Most species only occur at depths visited by research submersibles.  It is illegal to collect Hawaiian corals without a special permit.