These handsome fellows are convict tangs (a.k.a. surgeonfish or manini). This large school was swarming the reef in order to graze on patches of algae. The schooling helps them get to the food which is normally guarded by other reef inhabitants. Since the other reef fish find it quite the task to chase away so many invaders at once, it's a feeding WIN for the tangs.
Technical Details Aperture Value: f/3.5 Focal Length: 7mm Exposure Program: Auto ISO: 64 Shutter Speed Value: 1/250 sec Location: Manauma Bay, Hawaii