I know mine are unbelievably painful due to endometriosis and PCOS. Mine have me laid up for days, throwing up from the pain at times. Even without endometriosis or PCOS, most women have painful or uncomfortable cramping. A pool may alleviate a bit of the pressure, but warm water is best like a warm bath or hot tub. The warmth helps relax the muscles that are contracting and giving you the pain. A heating pad works wonders along with an anti inflammatory like ibuprofen to help with any swelling and pressure.
