Why does skin wrinkle in water?
The short answer
Water immersion does more than simply swell the skin; nerves can constrict blood vessels and change the surface shape.
How it works
In fingers and toes, narrower blood vessels slightly reduce volume under the skin and create folds. The pattern may help grip wet objects.
A familiar example
Wrinkles are especially visible on palms and soles because of their skin structure and nerve supply.