Water birth

[Qasidy]

I was thinking about water birth and just can't help but wonder about whether water goes inside you as you are dilating, isn't that a risk if water is gushing inside the hole and your body, if it does go in where does it stop inside? And does it come back out again she you get up, sorry if this is a stupid question

It's no different to how it is when you have a bath ect.

It's your cervix that dilates. Not the actual opening to your vagina. So no more water than normal will go in.
Your cervix is open during a period, so no different to having a bath then