I think the thing is this- your body has to stretch, and be that in water or out- it's going to stretch. Waterbirth HELPS with pain in many women and even relaxing that area and keeping it supple, however water is also dehydrating and over extended periods of time can dehydrate that area, too.
I didn't know this. I assumed that being in water softens you continously. At least that is what those waterbirth books describe. Is it good to get out of the water every so often to prevent this? I am not pregnant yet, but am still nervous about labor and delivery pain, from what I have heard from others and seen on those TV shows like "Deliver Me" and "Birth Day" on Discovery Health.