Police were called to Eastbourne Pier around 4.10pm to a man who had fallen onto the beach.
Ambulance was called and the man was being treated for a serious head injury and he was flown to hospital in a life threatening condition.
The Health and Safety Executive has been informed as the man was working on the pier.
More top news
The High Court has agreed to a Sussex Police request for access to footage of the Shoreham air crash, but has rejected two other requests.
Wednesday's weather for the east of the region
Wednesday's weather for the west of the region