I'm a midwife, and very partial to waterbirths. The water can get pretty ooky, especially with the placental delivery.
It is not a big deal for most people, but some women (or their partners) are just squeamish about it.
If you think you might be, ask your midwife about getting out before the placenta.
Most midwives prepare a spot on the floor right next to the pool, anyway, in case they need to get the birthing mom supine quickly.
But, honestly, its not as bad as you may be thinking.