Interesting question. Other than your skin getting "pruney" from being in the water I'm not aware of any other problems it can or would cause. I life guarded and managed pools from late high school through college and spent a lot of time in the water. The only "problem" that I had was, for some reason, I was always incredibly horny after being in the water. Maybe it was seeing all the girls at the pool, I don't know.
On several occassions I had the pleasure of shagging my high school girlfriend after swimming at a local public indoor pool with her. Again, maybe it was just the fact of seeing her in her bikini and playing around in the water together, but it sure felt good when we'd do it right after swimming. I don't recall any problems at all from the water exposure.