Emergency services rushed to the scene in Rosslare Harbour in the early hours of Sunday morning after a man entered the water near the pier there.
The man, a Lithuanian national in his early sixties, was returning to the vessel he was working from at around 4 a.m. when he fell through the gap between the boat and the wall, landing in the water.
Workers from the Stena Line ferry spotted the man entering the water and immediately rushed to his aid.
They attempted to pull his body from the water using a lifebuoy and he was eventually transferred to the Rosslare Lifeboat. Despite the best attempts of Stena staff, RNLI volunteers and paramedics with the National Ambulance Service, the man could not be resuscitated and was pronounced dead at the scene.
The address given for the man was on board the boat, which suggests that he was only working out of Rosslare.
A spokesman for Wexford Gardaí said that they are treating the matter as a tragic accident and that the Coroner's Court will determine a cause of death.
This is the second Lithuanian national to lose their life at the port in recent months after a man in his early twenties died in a workplace accident on board the Irish Ferries ship 'The Isle of Inishmore' at the end of March.