A 48-year-old man has been airlifted to hospital after he suffered a serious spinal injury whilst swimming in the Hawkesbury River.

It is understood the man was diving into the water when he hit a sandbank and was knocked unconscious.

Bystanders pulled the man from the water and began administering CPR.

CareFlight’s rapid response helicopter was tasked shortly before 1pm, landing at a nearby oval.

NSW Ambulance paramedics provided initial treatment for the man.

CareFlight’s specialist doctor and critical care paramedic then intubated the patient at the scene, placing him in an induced coma to stabilise him.

The patient was airlifted to Royal North Shore Hospital in a serious but stable condition.

NSW police also attended the scene.