Here is an extract from The Yoga Journal about water therapy.
Bathe In It*
When you add a bit of art, science, and ritual, taking a bath is much more than getting clean—it's balneotherapy. A form of therapeutic bathing, balneotherapy has been practiced since the days of the ancient Greeks and Romans to preserve health and treat a range of ailments from injuries to eczema. Like yoga, it's also a great way to melt away stress and bring the body back into a more balanced state. "Submersion in warm water calms the physiological part of the fight-or-flight response," says Jonathan P. DeVierville, vice president of the International Society of Medical Hydrology and Climatology and director of the Alamo Plaza Spa in San Antonio, Texas. In other words, as you soak in the tub, your blood vessels dilate, your circulation increases, your muscles relax, and your nervous system chills out.
So, you can see why being in water, preferably in a bathtub, but also in a shower, positively affects a birthing mother...the fight-or-flight response is calmed, which means mom & baby are relaxed & have endorphins running throughout their bodies. Ahhhhh....