Growing up, my dad told me a story. He had a friend who was a trained diver. He was on a crew to clean and inspect dam turbines . He went down (Oahi Reservoir, Missouri River SD). They took an underwater camera with them record damage and what not. When they got to the surface and watched the video, they seen shadows of fish big enough to swallow a man. He quit his job and to my knowledge, has never got back into the water. My guess is that the fish he saw were spoonbill catfish. Still that's just nuts. Freshwater fish that can be that big.