A 15-year-old boy who was rescued from Lough Sheelin on Tuesday afternoon has died in hospital.
The boy was swimming in the lake, which is located at a meeting point of counties Westmeath, Meath and Cavan.
He was rescued from the water shortly before 3pm on Tuesday and taken to CHI Temple Street, where he died yesterday evening.
His death brings to five the number of people who have drowned in separate incidents in lakes this week.
A 13-year-old boy died in the Canal Court area of Scarva, Co Down, on Monday, after he got into difficulty in the water, while swimming with friends.
On Wednesday evening, a 29-year-old woman died in a drowning incident on the Longford-Cavan border.
It is understood that the mother-of-two got into difficulty while attempting to assist one of her children who was in the water at Swan Lake outside Gowna village.
She has been named locally as Natasha Core, who was from Gowna.
In a separate incident, a man in his 70s drowned in Co Leitrim, on Wednesday night.
The alarm was raised at Spencer Harbour, Drunkeeran, when the man who was snorkelling failed to return.
His body was recovered from the water a short time later by local emergency services.
In Northern Ireland, a 55-year-old man died following an incident in the Lough Melvin area of Co Fermanagh on Wednesday morning.
Irish Water Safety has said the majority of water tragedies occur in inland waterways and has emphasised the potential dangers of swimming in rivers and lakes.
Meanwhile, the Irish Coastguard has asked people not to swim alone and to avoid using inflatable toys in the open water, as it records a significant rise in calls outs and a rise in activity on the water.
Speaking to RTÉ's Morning Ireland, Gerard O'Flynn, operations manager with the Irish Coastguard, said the Coastguard has responded to 1,690 incidents this year to date, compared to 1,340 at the same time last year.
He said that "the excellent weather combined with restrictions on other recreational activities" has led to more people in the water.
Mr O'Flynn also urged jet ski users to be sensitive to other swimmers and asked people to "never ever, ever use inflatable toys on the water".
He said the increased popularity of open water swimming has many people swimming longer distances and he called on people to make sure they are visible in the sea by wearing a cap and a toe-float.
He said that people should swim in lifeguarded areas or areas that are commonly used.
The ESB has reminded people of the dangers of swimming in reservoirs. It said: "These areas are not appropriate for swimming because of the risk of deep and fast-flowing waters, changing water levels and uneven ground."
