It was not immediately clear how the 30-year-old diver injured herself.
The woman, whose name was not released, was pronounced dead shortly after she arrived at Jersey Shore University Medical Center in Neptune. She had been flown there by a helicopter crew from Coast Guard Air Station Atlantic City.
A crew member aboard the Gypsy Blood, a 122-foot dive boat based in Brielle, had called the Coast Guard around 11:20 a.m. to report that the woman had not resurfaced and had been missing for about 35 minutes.
A dive master aboard the boat soon found the woman under water.