Anyone who has taken a long bath or gone for a swim can attest to a certain pale pruniness of the skin that goes away harmlessly after a little while. And anyone who has spent a day at the beach splashing around can vouch for the fact that you get unduly fatigued from it all.
The answers are pretty interesting: did you know that your skin is water proof! I myself had never thought about it until now but truth be told none of us soak up water like a sponge. The reason is that the sebaceous glands in your skin produce an oil called sebum (SEE-bum) that acts effectively as water-proofing while also lubricating and protecting your skin. We tend to think of ourselves as walled off under our skin but it is actually this sebum that keeps us from bloating up with water every time we get into the pool.
When you go swimming, you lose this protective layer and your skin suddenly becomes more porous. Perhaps you remember the concept of osmosis from high school biology. Well, essentially, without that protective layer, the lower density of water in your skin relative to the pool, pulls water molecules into the top layer of your skin and stores it in your fat cells, via osmosis. This process tries to balance the water pressure difference between you and the pool and stopping at saturation point (i.e. wrinkly pruny skin.) This layer is attached to the layer below that does not absorb water and the combination of being fixed down and the increase in size of the top layer leads to wrinkly skin.
An interesting aside is that swimming in the ocean, whether just a quick jaunt or a dive for pearls, will never leave you pruny and water-logged. Why? Well, it goes back to osmosis. When you are in a pool, the salt concentrations of H2O in your skin are higher and so the water from outside goes in. Well, when in the ocean, the salt content in the sea water is much higher and therefore draws the water in your skin, after the sebum has rubbed off, out into the ocean. Can you imagine? Your body trying to equalize the salt content of the ocean? That’s a lot of water to give off. So…
This highlights the important fact that should be remembered in the Summer when you are making a trip to the beach. If osmosis is working against you in salt water (taking water from your skin cells), then you need to counteract this by drinking extra water or a drink like Gatorade that is full of electrolytes. Doctors suggest about 8 cups of water a day, more if you are going to be active. We suggest 15 cups of water to drink a day, which is roughly equivalent to about 10 cans of soda. This might seem a lot but just remember that with the combination of that sun beating down on you, and the salt water sapping H2O from you, it’s crucial that you stay hydrated while having fun in the surf and sun!