Random Videos on Instagram: "The way seals sleep underwater is a fantastic example of a marine adaptation that blends instinct with physical necessity. Seals are mammals, so they must surface to breathe, but they don’t have to fully wake up to do it. They often engage in unihemispheric sleep, meaning they shut down one half of their brain while the other half remains lightly active. This allows them to maintain a level of awareness necessary to paddle up for air and to keep an eye out for predat