Typical modern day Hollywood, where none of the actors have visible nudity in their contracts. All implied. You know what is happening, but the view is always obscured.
A girl and her boyfriend are shown during intimate moments several times. They kiss, lie in bed, and have sex throughout the movie. They are naked or semi-naked more than once: the girl is seen wearing underwear, while the guy is seen shirtless. The girl's butt is shown once.
There is a rather explicit sex scene at the beginning of the movie, involving full nudity, orgasm and oral sex. A girl and guy are having sex; she indicates for him to tell her 'when' meaning when he's about to finish. He does and she then pulls off of him and proceeds to give him oral sex (implying she swallows as he was just about to finish). There is another shorter one later on. However, no graphic nudity and details are actually shown.
In a flashback, man is visiting S&M club where a few fetishes occur. They are not graphic though.