Man and woman sex scene

Hi.
Maybe in year 2000-2010, in what I remember, I saw this movie about a man in a university with some kind of research about sperm so he tried to find a volunteer about his research so he eventually find a woman ( i think it was his student or not). The only scene i remember most is when this man and woman where playing in the beach (rolling over and over and some kissing), they got back at a house they were joking about something (i dont know really) while this woman tidying up after she went to shower. And then the guy said (not really word by word in the script but u get it) “but I saw some sand on your back while running”, and the woman said really and asked the guy to take it off from her back and then they have sex.

I also think it was a not an american movie. Pls help. Thanks 🙂

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