There's not too much goo, you will be out of the bath before the placenta arrives.

The water makes the skin easier to stretch, which is good with bigger babies and reduces your chance of tearing.

The baby wont breathe until it feels the air. So when you are pushing you have to have your butt under water, and the baby can stay under water as long as the cord is still pulsating because they are getting oxygen from you.

If you find water relaxing, then have a waterbirth.