Hippos secrete a pink, natural sunscreen from their skin.
You should limit the amount of time you spend in the sun between 10 am and 4 pm. It's good to wear a hat with a wide brim when you're out in the sun. The earth has a protective shield, the stratospheric ozone layer, that protects us all from the effects of UV radiation. Out of every 10 million air molecules, about 2 million are normal oxygen, but only three molecules are ozone. The higher the UV Index number, the more sun protection you need.