Eating backswimmers or water boatman maybe. That's my first thought. You can find patterns for both online. In a pinch a size 12 Prince is a good choice. This is on the small size for a backswimmer and large size for a water boatman. Both bugs usually have a air bubble about them. the white biots on the back of the prince sort of gives a bright spot fish may interpret as a bubble. You can fish through the water column. Floating, intermediate, or sinking lines. Erratic 2-4 inch strips with pauses. Grabs with the fly just under the surface can be pretty exciting.