>>936805697It's not water tight, but it is closed.
Sometimes water can go in but they have to move in a weird way to cause a pressure difference to suck some in.
Or, if they find one of the jets and sit on it.
A normal bath or swim session will not cause water to go in.
Vaginas are very sensitive to change, especially in ph (acid) levels, so they are designed to prevent this to a point.