Another world only you and I know

Hope( 13 year old ) was at a pond, she was sad, thinking that her crush would reject her after she tells him that she likes him. But her best friend, Justin( 14 years old ) goes to comfort her. Yet only minutes later hope falls into the pond and gets stuck at the bottom, thrashing around she tries to free herself and screams, then she realizes that she's not even drowning...she can talk under water...and breathe...how is this even possible? Then after Justin goes to "save" hope they find something shocking and end up in another world that only they know.