Why is humans skin waterproof?

Humans do not have waterproof skin. Our skin is semi-permeable, which means that only some water molecules can pass through it. For this reason, we can become wet when exposed to water. Water can also pass through our skin through sweating and evaporation. Humans do have a layer of oils on their skin that can form a barrier against water for short periods of time, but it is not a perfect seal.