Thousands of fish, frozen in mid-air while apparently leaping out of a South Dakota lake, made internet headlines. However, the iced-up fish were actually victims of falling oxygen levels, caused by snow on the frozen lake surface blocking sunlight, and preventing aquatic plants from photosynthesising. Dead from suffocation, the fish floated to the surface. Very cold weather then made the ice expand. As it reached the shore, the ice cracked and pushed skywards, taking the trapped fish with it.