Why does our skin wrinkle when we put our hands and feet in water for a long time? It is because the skin on the palms of our hands and the bottom of our feet is thicker than other parts and when they remain in water for a long time, the cells in the skin soak up water and swell up. The surface area of the skin expands significantly. However, the dermis or the inner skin layer remains unchanged. This forces the surface of the outer skin or the epidermis to wrinkle.