Why Do Our Fingers Wrinkle in The Bath
Our skin is like a suit of armour which keeps germs and dirt out, and our body fluids in. But it's not completely waterproof. The top layers of our skin are made of dried out, flattened dead cells and if you make the skin wet for any length of time, some of the water starts to seep into the dead cells and makes them swell up and form wrinkles. The effect is most noticeable where our skin is thickest for protection, such as on our feet or on our hands. You see wrinkles because as the water seeps into the skin it makes it expand, and rather like railway lines buckling on a hot day, the skin is pulled into a series of ridges and troughs. Fortunately, it's not harmful and drying yourself off, or removing the offending boots or trainers, usually makes it go away quite quickly.
In 2013 UK scientists discovered that fingers go wrinkly in water to improve our grip on wet or submerged object. They also showed that it is in fact constricting blood vessels, not osmosis, that drives this change.