It happened around 11:30 Saturday morning at Brendan Byrne State Forest in Pemberton Township.
Police say a skater found the body in a frozen pond in the Whitesbog Village section of the forest.
Authorities are awaiting an autopsy to determine the victim's cause of death. No word on the man's identity.
Anyone with information is asked to contact New Jersey State Police at 1-609-859-2282.