The substance that makes skin water resistant is sebum, an oily substance secreted by the skin's sebaceous glands.

Here's how it works:

* Sebum forms a protective layer: Sebum coats the surface of the skin, creating a barrier that prevents water from penetrating.

* Hydrophobic nature: Sebum is hydrophobic, meaning it repels water molecules.

* Moisturizing effect: Sebum also helps keep the skin moisturized, which further contributes to its water resistance.

While sebum plays a major role, the stratum corneum, the outermost layer of the skin, also contributes to water resistance. This layer is made up of dead skin cells that are tightly packed together, forming a barrier that prevents water loss.

So, it's a combination of sebum and the stratum corneum that makes our skin water resistant.