A notoriously dangerous beach on the NSW north coast has witnessed another tragedy after the death of a swimmer.

Emergency services were called to Tallow Beach, near Byron Bay, around 12:30pm on Wednesday, following reports that a man was in trouble in the surf.

Tallow Beach is not patrolled and regarded by locals as challenging.

A 21-year-old man from Brisbane was found face down in the water by a surfer who brought him to shore.

A NSW Ambulance spokesman said a bystander was performing CPR when paramedics arrived. They continued CPR for another 30 minutes but were unable to revive the man.