Witnesses told police a shark attacked the 17-year-old at Wilsons Headland at Wooli Beach, north of Coffs Harbour, just before 2.30pm on Saturday.
Board-riders helped the boy to shore and he was given first aid for serious leg injuries but died at the scene despite efforts to resuscitate him.
Beaches in the area, including Wooli, Diggers Camp and Minnie Water, have been closed.
Clarence Valley Mayor Jim Simmons says visitors had flocked to the region for the school holidays and there would likely have been many people in the water.
“What’s happened there this afternoon would shake everybody,” Mr Simmons told AAP.
“It’s terribly shocking.
“All of our sympathies, from people in the area, go out to the boy’s family.
“I just ask people to look out for their safety on the beaches.”
Police will liaise with the Department of Primary Industry to investigate the circumstances surrounding the death and a report will be prepared for the coroner.
