The accident happened just after 12.30pm at Leenan Pier close to Clonmany.
The man has been named locally as John ‘Ned’ Kearney form Urris.
The Greencastle Coast Guard and Ambulance services rushed to the scene while Malin Head Coastguard Station was also contacted.
A rescue helicopter was dispatched shortly afterwards to take the man to hospital.
However the victim was pronounced dead at the scene.
A spokesman for the Gardai said the incident is being treated as an accident.