Sunday night, my science grad student friends were all gathered around the hot tub, and we noticed that our hands were wrinkled. So we all attempted to figure out why your hands get wrinkled after being underwater for a while.
Being brilliant scientists, we assumed that some sort of osmotic effect was causing our hands to dehydrate. However, we couldn't figure out how reverse osmosis was occuring since the cells in your hand have a higher salt concentration than the hot tub water. In fact, one quick google search later, I found that biologists claim the cells in your skin swell with water when submerged in a pool or hot tub as osmosis would dictate. The result of the swelling is your skin stretches and forms wrinkles. So, we were right about the osmosis and wrong about the skin dehydrating.
(Note: In the rare event that someone without a science background ever reads this post, here is a basic explaination of osmosis.
Two solvents with solutes separated by a semi-permeable membrane. A semi-permeable is a membrane that allows a solvent (ex. water) to move freely between the two liquids, but not a solute (ex. salt). In such a system, the solvent will spontaneously flow from the lower solute concentration to the higher solute concentration until the two concentrations are equal. This process is Osmosis.)