Where she fell

Teenager Eliza and her friends are going to explore a cave near their upstate New York home, but first her friends insist on dragging her to Drowner's Swamp. It's a place which her mother has frequently warned her about. When the earth opens up and swallows Eliza she finds herself in a system of caves. What she finds living there is strange and dangerous beyond any of the stories she has heard about in the past.