The man, in his 20s and from Co Armagh, was pulled from Lough Ree in Co Westmeath in the Irish midlands after the boat he was in with two others capsized yesterday afternoon.
One other man remains in a critical condition in hospital and a third man is still missing.
Gardai confirmed the man died after being transferred to a Galway hospital on Thursday night.
The search for the third man resumed shortly after 8am on Friday.
The search is being carried out by Lough Ree RNLI, sub-aqua units from Athlone and Lanesborough and local anglers are also taking part.