Why do our fingers wrinkle in water?

Scientists think that they have the answer to why the skin on human fingers and toes shrivels up like an old prune when we soak in the bath. Laboratory tests confirmed a theory that wrinkly fingers improve our grip on wet or submerged objects, working to channel away the water like the rain treads in car tires.

Wrinkled Fingers | Source: Quora

These dead keratin cells in the stratum corneum absorb water easily and start to swell after extended periods in the water, but the living keratin cells deeper in the skin do not. As the dead cell layer expands, it begins to take up more surface area, but it's still connected to the living cells beneath and doesn't have anywhere to go. As a result, the stratum corneum wrinkles to give the temporary new surface area someplace to go [source: Library of Congress]. Researchers are studying other theories for what might help cause the wrinkling, such as the whether the constriction of blood vessels is related to it.