Why does water roll of a persons skin when you get out swimming pool?

The phenomenon of water droplets forming spherical beads and rolling off the skin when we get out of a swimming pool or take a shower is known as the " Leidenfrost effect."This effect occurs when a liquid comes in contact with a surface that is significantly hotter than its boiling point.

Formation of vapor barrier:

When water droplets land on the hot skin, they immediately start evaporating creating a thin layer of water vapor between skin and the droplet. This water vapor acts as a barrier, preventing the direct contact of the water with the skin, making it roll off in spherical shape while still in its liquid state.

Sphericity:

The spherical shape of the water droplets helps in reducing the surface area of the water in contact with the hot surface. This lowers the rate of heat transfer between the skin and the water preventing it from boiling rapidly and maintaining the vapor layer.

Skin temperature:

To observe the Leidenfrost effect, the temperature of skin should be above water boiling point ( 100 degrees Celsius at sea level). Usually human skin temperature is around 37 degrees Celsius, But after prolonged immersion in warm pool or shower, skin temperature can be high enough for this effect to occur.

However, it's worth noting that the Leidenfrost effect is a very transient phenomenon. Once the water droplet has rolled off or evaporate fully, the skin will come into direct contact with the air, leading to the sensation of coolness or evaporative cooling, which helps lower the skin temperature back to its normal level.