Female breast is seen in passing in the first episode. This is during a sex scene. No other nudity in this scene.
There is regular reference to sex throughout the show, most of it implied. Some sex scenes are depicted with implied nudity or visible bottoms.
There is one scene in Season Three involving a female character masturbating while fantasising about having sex with a male character. Her hand can be seen moving underneath her panties but nothing else is shown. In the fantasy sequence her breast is seen briefly, with nipple visible.