Sunscreen is a lotion, spray, gel, or other topical product that helps protect the skin from damage caused by the sun's ultraviolet (UV) radiation. It is formulated with ingredients that absorb or reflect UV rays, preventing them from reaching the skin. Sunscreens are typically applied to exposed skin before going outdoors, and they should be reapplied throughout the day, especially after swimming or sweating.

Crayfish have a natural sunscreen that helps protect them from UV radiation. This sunscreen is produced by the crayfish's hepatopancreas, which is a gland that is responsible for producing digestive enzymes and other important substances. The sunscreen produced by the hepatopancreas is made up of a variety of compounds, including carotenoids, flavonoids, and mycosporine-like amino acids. These compounds absorb or reflect UV rays, preventing them from damaging the crayfish's cells.