A major rescue is underway after a teenager was swept away by a large wave this afternoon.

The teen was caught in heavy surf off Warriewood in Sydney’s north just after 1pm, with rescuers initially losing sight of him in the rough conditions.

He was later spotted inside a coastal cave, sparking a complex rescue operation.

Emergency services, including surf lifesavers, are working to reach the boy as challenging conditions continue.

It’s understood the teenager is conscious but has suffered injuries.

Rescue crews search rough surf after a teenager was swept off the shoreline at Warriewood, with the teen later spotted inside a coastal cave.Rescue crews search rough surf after a teenager was swept off the shoreline at Warriewood, with the teen later spotted inside a coastal cave. Credit: 7NEWS Emergency services work in challenging conditions as they try to reach the injured swimmer.Emergency services work in challenging conditions as they try to reach the injured swimmer. Credit: 7NEWS