Our skin is able to maintain itself even after hours of soaking in warm/cold water. Cells begin to swell as they soak up water and our outermost layer of skin doubles or even triples in size, causing our skin to wrinkle. However as we become older, our skin becomes thinner. Even though the outer layer of skin can still swell, there is less swelling and therefore produces less wrinkles.
The main reason skin gets wrinkly instead of dissolving is due to the structure of keratin in the outer layer of skin cells. The keratin filaments in these outermost are arranged in a net-like pattern. This outer layer is still anchored to the layer of skin beneath it, which does not absorb any water.
So you can thank keratin filaments for making sure we remain intact and don’t dissolve like the wicked witch west!