Wake (Watersong #1) by Amanda Hocking - 2013-04

Gemma Fisher seems to have it all--she's carefree, pretty, and falling in love with Alex, the boy next door. He's always been just a friend, but this summer they've taken their relationship to the next level, and now she's falling harder for him every day. But Gemma doesn't know that her ordinary life is about to change forever.

Penn, Lexi and Thea are strangers in town for the summer--and they've been watching her. Three sisters with mysterious powers, they invite Gemma to join their exclusive circle, and it changes her in ways she never imagined. Suddenly she's stronger, faster, and more beautiful than ever. But her new powers come with a terrifying price. And as she uncovers the truth, she's is forced to choose between staying with those she loves--or entering a new world brimming with dark hungers and unimaginable secrets.