A professional diver and a 7-year-old boy were drowned in two separate coastal accidents over the weekend.
Mr Damien Byrne (24), from Cabinteely, Co Dublin, drowned when he got into difficulty during an underwater salvage operation near Dún Laoghaire on Saturday evening.
Mr Byrne had recently qualified as a professional diver and was working for a diving company when he died.
He was part of a three-person diving team which was working a mile off the Dún Laoghaire coast, where a yacht had sunk earlier that day.
Mr Byrne and his colleagues were working underwater to prepare the yacht for re-floating, and were believed to be in the process of attaching cables to the vessel.
According to diving sources, Mr Byrne got into difficulty when equipment became entangled. His two diving partners freed him and brought him to the surface.
He was brought to the shore by the Dún Laoghaire Lifeboat and taken by ambulance to St Vincent's Hospital, where he was pronounced dead on arrival.
Yesterday, Mr Liam Finnegan, of the Irish Underwater Council, the representative body of diving enthusiasts, said the Irish diving community was in dismay about the accident.
"First and foremost, we would like to express our deepest sympathy with the family of Damien Byrne," he said.
"It's a bad day for the diving community in Ireland. Damien wasn't a member of our organisation, but it's a small company and we all know each other."
Mr Byrne is the first diver in six years to die in Irish waters.
Mr Nic Gotto, an experienced diver, died in 1998 while bringing a group of people on a tour of the Kowloon Bridge wreck off the coast of Castletownshend, Co Cork. Questions have been raised by his family about whether the breathing apparatus he used was a factor in the accident.
In 1996, a 32-year-old man died while learning how to scuba dive in shallow waters in Co Mayo.
The 7-year-old boy who drowned at Balbriggan, Co Dublin, on Saturday morning, was named later as Karl Moore of Inbhir Ide, Malahide.
He was found in the sea less than an hour after he was reported missing.
He had been staying with his aunt in Balbriggan when, it appears, he wandered away from her house.
She reported him missing to gardaí in Balbriggan almost immediately and less than an hour later his body was seen floating in the sea off the beach.
A post-mortem will be carried out today.
Meanwhile gardaí are investigating the death of a man in his 40s who was fatally injured after he fell more than 50 feet down a cliff face after leaving a party in the early hours of yesterday morning.
It's understood that the man had left a party at a house in the Grattan Hill area, off Lower Glanmire Road, when he fell over the cliff face and landed in a playground at O'Mahony's Avenue at around 4.45 a.m. yesterday.
The man - who hasn't been named but is understood to be from Cork city - was taken by ambulance to the South Infirmary where he died some time later. A post-mortem examination will be carried out at Cork University Hospital later today.