Dead River:

Dead River By: Cyn Balog
Fiction: Paranormal, YA, 242 pages
Physical Book Count: 76
Book Count: 93

Ki's dad moved her out of their house by a river and never let her anywhere near large bodies of water after her mom killed herself in a river when she was 7.  So of course the 1st time he lets her go off to a river, it's the Dead River, with a couple of friends when she's 17, because that sounds realistic.  When there she learns more about the water and the "imaginary" friends that she had when she was little.