it depends on the amount of dissolved solutes in solution. human cells are approximately 290mOsm/L. In a pure liquid, osmotic gradient will force water into the cell to dilute the intracellular space and your cells will swell and explode. What most likely happens here and in the tub, pool ect is the water has more dissolved particles in it (from minerals, ions and random bullsh, or in this alleged case lots of fermenting glucose in the vaginal wall secretions) that tend to draw water/moisture out of the cells and into the enviornment causing a wrinkled appearance. hypertonic solutions are less likely to lyse cells.