Have you ever wondered, why you always have wrinkles on your fingers during long hour in the water?
Some people think that wrinkling is the result of water passing into the outer layer of the skin that caused the swelling of the skin.
According to the research, the pattern of wrinkling appeared to be optimized for providing a drainage network that improved grip. The fingers give a better grip in wet conditions. It is like treads in car tires that allow the tire to be in contact with the road and gives a better grip.
The same effect with the toes, the wrinkles, help the toes to get a better footing on the wet floor.