Sussex Police said officers were informed by HM Coastguard that a man had been recovered from the sea after falling from a commercial fishing boat on Thursday (July 29) at about 10am.
He had been airlifted to Eastbourne District General Hospital but had sadly died there, a police spokesman said.
Police added: “His next of kin has been informed and enquiries are ongoing.”
The coastguard said its helicopter from Lydd and RNLI lifeboats were called to a ‘mayday broadcast’ related to a fishing vessel with two people on board, south of Hastings at 9.30am.
A Maritime and Coastguard Agency spokesperson said: “At 9.30am today (29th July), HM Coastguard received a report of a Mayday broadcast from a fishing vessel with two people onboard, south of Hastings.
“The coastguard helicopter from Lydd and Hastings RNLI lifeboats were sent to assist.
“One casualty from the vessel was flown to Eastbourne Hospital.”