When in a male
communal shower situation, like high school or jail,
one or more of the men
masturbate, then ejaculate on an unsuspecting bather. This will usually occur on the outer thigh or buttocks areas, but if the ejaculator has enough force, it can wind up on the upper back or scalp.
A lesser Saskatoon Shower involves getting urinated on in the same manner. It is conceivable that women can initiate an S.S. if they can ejaculate wit the proper trajectory and velocity.