A member of the public noticed the incident and contacted emergency services on Saturday afternoon.
A large search was then launched for the missing teenager, involving local surf rescue personnel and the Westpac Lifesaver Helicopter, but the boy couldn't be found.
"The members of the group are family members, they're known to each other, they're visiting Coffs Harbour for the Easter weekend," a police spokesman
A search will resume at first light for a teenage swimmer who disappeared in rough surf off Pebbly Beach. #9Newspic.twitter.com/ZN9IrVFTXm
Another member of the group of swimmers, who was taken to Coffs Harbour Health Campus after inhaling a lot of water, is expected to make a full recovery.
An even larger search is due to commence on Monday, with police divers assisting the effort.