But scientists are still working out exactly how these ancient Loch Ness Monsters got around. Everyone agrees that they swam—their massive, turtle-like flippers wouldn't have been good for flying or clomping along on land. But researchers disagree about whether all four limbs participated in propulsion, or if just the front two did most of the work. To figure it out, scientists at the University of Southampton built a robotic replica of these flummoxing flippers. And in their model, at least, the use of all four is the most efficient way of moving about.