A local's advice about weather patterns was the key to rescuing a teen surfer who was swept to sea and later found alive 13km off the coast on an island.

Locals and authorities began searching for Darcy Deefholts, 19, early on Thursday morning after he was reported missing on Wednesday afternoon.

The young man had last been seen fishing in Wooli in northern NSW, before he left his clothes and bike at a nearby beach and went for a surf and did not return.

It sparked a search effort that endured into the night, and his father, Terry Deefholts, made a desperate callout for assistance.

While marine rescue combed a 15km stretch of the sea, Mr Deefholts received information that proved critical in locating his boy.