709.9  Indecent exposure.
  A person who exposes the person’s genitals or pubes to another not the person’s spouse, or who commits a sex act in the presence of or view of a third person, commits a serious misdemeanor, if:
  1.  The person does so to arouse or satisfy the sexual desires of either party; and
  2.  The person knows or reasonably should know that the act is offensive to the viewer.
[C79, 81, §709.9]

Definition of sex act, §702.17