I have seen strange things. Sometimes it challenges my skill to photograph what I have seen. The fish are schooling. The are maybe 10 to 12 inches in length. They appear in the distance. What you first notice is the sparkle of the water glittering silver as the mass swims in a large circle toward you. No time to adjust. You just hold up the camera and hope something is in the image you just took. It’s very weird. These fish are swimming open mouthed. The water can be seen through their gills.
They look to be on rampage and could cause serious harm. But they seem to be merely swimming. They do not appear to be feeding nor do they appear to be fleeing a larger fish.
I’ve seen this once before and this time I was somewhat more prepared. But to adjust exposure and focus on the fly is very hard to do. You are at once fascinated by the behavior and trying to play with all the dials on the camera. Meanwhile the fish swim out of the range of your camera in murky water.
Well, you can see the open mouths. What it all means is not for me to guess. Without their mouths open this school is just plain invisible on the reef. Open mouth and wow!