Every so often whilst diving you see something in the distance and your immediate reaction is "what on earth is that". Distance can distort scale and shape underwater and an unusual angle on a large item can really weird you out (I memorably once mistook 2 humpback whales for 6 enormous squid - the scale and distance was just too much to comprehend (nb the whales were not small but were far away). Anyway the point of this post is to show you this school of bumphead parrotfish which my buddy and I were bewildered by on a Barrier Reef sunrise dive. Having established it was neither something huge and dead (her) nor a ghost net (me) we got a chance to check out the bumpheads up close.
Bumpheads can be huge fish but they are usually seen in these big schools. They eat hard corals and process it releasing pure coral sand later (that white sand beach you loved? fish poo) and they do so as a great herd wandering over the reef especially in the early hours devouring huge chunks of reef. When they're not doing that they tend to float near the surface in these enormous defensive balls. Either way they make one of the most remarkable sights in the underwater world.