First, if after reading the book description you are expecting to read a paranormal romance involving mermen or other mythological creatures, you are going to be disappointed. Please don't let that stop you from reading this book, though! Marissa has recently broken up with her cheating live-in boyfriend, has crazy parents, and has other issues from her past which become important as the story progresses. Trying to escape her life for a few minutes, she takes a trip to the beach and falls asleep. As the tide comes in, she is swept out to sea, pulled by a strong undertow, becomes trapped under some debris, and almost dies. Marissa becomes obsessed with the idea that a merman - or some other similar creature - has saved her.What follows in the rest of the book is a fascinating journey into Marissa's mind. Is she forever broken by the events in her past or can she find peace? Was the creature real or was it a desperate attempt by her mind to latch onto something better for herself?I was hooked right away. I liked Marissa and felt sympathetic towards her and her situation with her boyfriend and parents. Her relationship with her best friend and her new college roommate felt authentic. As I got a little further along, there were changes in Marissa's personality and behavior. At first I was a little thrown off by this and thought What the hell is going on with this girl? I started to dislike the character a little bit. And then the full extent of Marissa's reality emerges. All becomes painfully clear.I am reluctant to say too much because I don't want to give anything away but I found this book really fascinating. Now, I've never known anyone personally with the same issues that Marissa has so I cannot speak to the medical authenticity of the issues. However, Marissa's descent into psychosis was absolutely compelling. It was like a car wreck - horrible but I just could not look away. I loved the ending! Some might be disappointed because the author leaves things a little bit open to interpretation. I think it's that little extra something that earns this book it's fourth star. Recommended for older teens - 16+ at least! - and adults that love realistic fiction.