This is a video of a Great Blue Heron flying with a fish in it’s beak.
I have never seen a heron grab a fish in the middle of a lake. They are big wading birds that wonder along shorelines. They frequently stand still for extended periods and can be easy to miss, blending with limbs and vegetation. I spotted this particular heron hundreds of feet from shore flapping around in a frenzied manner on the surface of the lake. When it finally left the water it flew towards me and I could see it had captured a pretty good meal! It is a little tricky spotting the fish from the iPhone video but I would guess it was well over a foot long.