This is episode two of Swimming with Shadows: A Radiolab Week of Sharks. Jaws spawned a thousand imitators: sharks in tornados, sharks in avalanches, sharks that battle giant octopuses. Hollywood has officially turned sharks into monsters of every shape and size. And yet, somehow, there will always be more. But drop below the surface, into the cold, quiet blue, and another creature appears. One that has survived mass extinctions, outlasted ancient predators and pre-dates Mount Everest, the existence of trees, even the rings of Saturn. A shark that is somehow even more remarkable than sharks...