Black durgon

The black durgon is a member of the triggerfish family.  It has a black body that is accented by pale blue lines at the base of the dorsal and anal fins.  The blue lines are visible from quite a distance. This fish gracefully propels itself largely by moving its dorsal and anal fins.

When you get close to the black durgon, with the right lighting, it becomes apparent that the fish is not solid black, but a delicate pattern of lines and diamonds, with a yellow cast on the head, and pale blue lines through the forehead.

In the below photo, the trigger is visible, as the first dorsal fin.