The attack happened around 5:00 p.m. Saturday at Riverview Beach Park.
According to investigators, the 40-year-old victim was inside the port-a-potty when a man forced his way in and hit the woman on the head.
Then, police said, the man sexually assaulted her before running away.
The woman was treated for her injuries at a local hospital.
The suspect is described as a white man with a tan or olive complexion. He was about 5'6" tall with a thin build wearing a dark-colored jacket and dark-colored knit hat.
Anyone with information is urged to call the Pennsville Police Dept. at 856-678-3089.