The skin forms an elastic protective cover on our body. It consists of three layers; the upper layer of dead cells, the middle one of living cells and the lower most layers connected to muscles and fat. Normally the upper layer of dead cells acts as an effective water-proof barrier. But on prolonged immersion in water, the dry cells in the layer absorb water and swell. This causes the skin to form wrinkles which disappear when the skin dries out again.