A 29-year-old man was airlifted to hospital on Sunday afternoon.
The man, who is from Pembroke Dock, collapsed on Pendine Beach after he was involved in what coastguards have described as a 'prank that went wrong'.
The man had apparently been riding on the roof of a car being driven along the beach when he fell off and hit his head on the sand.
The car was being driven at approximately 15 mph by a 19-year-old male person, also from Pembroke Dock, at the time of the incident.
As a result of hitting his head, the man suffered an epileptic fit and fell unconscious.
An ambulance was called and the assistance of the coastguard unit from Tenby was requested at the incident, which occurred at approximately 3.30 pm.
The man was attended to by paramedics at the scene before being flown by the Welsh Air Ambulance to Glangwili Hospital, Carmarthen.