Help me find this horror movie PLEASE?!
So, the movie starts with college friends together and one of them is having a sexy chat with a girl that has a tattoo. Later on what I remember is they all drive to a beach house with their professor, and then they all went to the beach first & he sees the girl he video chated with and recognized her by her tattoo on the video chat. The main character, one of these friends, has an ill brother,(also he wears glasses) drug addict that has a homeless looking friend, and perhaps he's imaginary as far as I remember. The mentally ill drug addict brother comes up to the beach house and the main character-his brother asks him to leave and not to cause any problems. (he's kinda ashamed of him). But he didn't leave, he started sneaking on them. One couple from this group of friends start making out in the beach house garage and the ill brother morbidly kills them both, I don't remember how. Also there are a lot of scenes with animated monkey i think, he talks with him, and that's the ill brother's imagination due to drug use. He started killing all of them one by one and the main character, his normal brother notices this and everyone was scared etc etc and he drugged them all by pouring the drug into their drink and they didn't notice it because he was very sneaky in the entire movie. I remember in the end professor that was with them tripped out at the beach, it was night and he saw indigenous people around him as hallucination and drowned himself in the sea because of it. In the end, this main character, the normal brother, runs with a girl in some kind of greenhouse but the mentally ill drug addict brother manages to find them and kills the girl as far as I remember. I watched this in like 2013 I think, I don't remember. Please guys help!!!!!! I'd really appreciate it.