In order to be effective in the hot sun and in water, sunscreens contain moisture-repelling substances and waxy compounds. It's generally these ingredients that make removing such stains a challenge. To eliminate the smudges from leather, blot with a clean, dry cloth. Then blot with a cloth barely dampened with hot water and a few drops of dishwashing liquid, continuing until mark is gone. Follow up with a cloth dampened with water to remove any traces of detergent.