A woman is taking a bath and all but her face is covered by bubbles. She stands up but her naked body is only visible from behind (and a little above) such that there is no frontal nudity.

A man and a woman have sex in bed. They are seen naked from the side but they hold each other close enough that no frontal nudity is seen. They have sex again later but they do it totally under the covers.

A couple has sex. We don't see much except afterward they are clearly naked. They are lying down and we only see their back side but we see their entire back side.