In Australia women are often encouraged to immerse themselves in a jacuzzi style bathtub right up until the crowning when most larger establishments do not allow waterbirths. However, correct me if I have my facts confused, but I have always been under the impression that jaccuzzi's (presumably with air bubbles) are to be avoided due to the possibility of air embolism which may occur via the opened cervix which can cause maternal death. Otherwise water immersion during labour seems to be very efficient in decreasing the amountof pain relief required during the labour.