Imaginary girls part 1

This book is pretty good so far. It is about this girl named Chloe whom lives with her sister in a small house near the mysterious reservoir which settled after a flood over the small town of Olive. One night Chloe decides to go to the reservoir with some friends for a late night swim. While taking on a challenge given to her by her sister to swim the reservoir end to end, discovers the dead body of one her classmates. She moves away and leaves everything behind, but when she comes back for the summer she sees her classmate alive and well. Now Chloe is tangled in her past and is trying to figure out. What is real and what is fantasy. This book is odd but that is what makes it interesting.