It s not hard to imagine where these moon jellies got their name. As delicate as they look, jellies are tough: They ve been around for 600 million years,predating sharks and surviving multiple mass extinctions, including the one that killed the dinosaurs. What makes jellies such survivors? Unlike fish, they re able to absorb oxygen directly through their bodies, storing it in their tissues so they can hunt in deep waters. Baby jellies can develop from swimming larvae directly into adults, but they often settle down and turn into polyps. Polyps can go dormant if conditions get bad, survive months without food, and even clone themselves.