Just when you think you are swimming serenly alone, you find yourself suddenly surrounded by a cloud of Baitfish. Just as this picture of the Sea Turtle, he was minding his own business and became enveloped by the Baitfish. The Baitfish are EXACTLY what the name implies. Bait. For bigger fish.
Credit for the photo—Diver/Attorney—Thanks R.E.C.! Credit for any big words I use–Attorney/English Professor—Thanks D.J.