1,105. How to Stand in the Mikvah

161:14 A woman should not immerse standing upright because there are places on her body that become concealed by doing this. She also shouldn't bend over too much so that parts of her body press against one another. Rather, she should bend over slightly so that her genitals are exposed, the way one stands when kneading the dough and spreading the legs slightly for a firm stance. The underside of her breasts should be visible as when she nurses a baby. She doesn't need to spread her thighs too much, nor spread her arms from the body too much. Rather, they should be as they are when she walks. If she bent over too much or stood too upright, the immersion is invalid because folds form on her body and the water can't reach those places. She must make sure that the water is above her navel by three handbreadths (about nine inches) so that she can immerse properly. In a case of need, if the water is not that high, she should first sit slowly in the water up to her neck, then immerse in a way that won't form any folds on her body outside the water. If folds formed on her body after she was in the water, it is of no consequence because the water already reached those places. If the water is very shallow, she can immerse lying down in a case of need. She must be sure that the water covers her entire body and all of her hair at one time.

161:15 The woman does not have to open her mouth to let the water enter, but she should not close it unduly tightly. If she did, her immersion is invalid. Rather, she should hold her lips slightly closed. If she had her hair in her mouth when she immersed, the immersion is invalid because the water didn't reach her hair there.