Big Eyed Scad (Hawaiian name: Acule) feed offshore on plankton at night, and tend to congregate in huge schools in shallow water for protection during the day. The baitball can be massive - as big as a house, hundreds of thousands of fish. If the water is clear and you can find the school, these are a blast to shoot. I've run out of air and camera battery more then once getting pictures like this.
This image was from last year, shortly before some local fishermen moved in and constructed a huge pen to fish the school out. They gave up without catching the scad, but stressed them enough so they disappeared. A year later, I've heard reports that small schools are starting to reform at different locations.
This pic is a small vignette of the overall baitball, taken before I equipped myself with wide angle capability. Just prepared it for a big print, so I thought I 'd post it as well.