Police say the girl from Morris County was found at the bottom of the pool at the Skyview Motel on Dupont Avenue.
Rescuers estimate she was underwater for two or three minutes.
A teenager who knew CPR tried to save the girl's life. Rescue workers rushed her to Community Medical Center in Toms River, where she was pronounced dead around 6:00 p.m.
It was not immediately clear how the girl got into the pool.
The pool had warnings that no lifeguard was on duty but it's not clear if any adults were keeping an eye on the girl.