It’s believed the man was seen diving into the water but not resurfacing.
The alarm was raised at around 6.30pm at Ballyalla Lake on the outskirts of the town of Ennis.
The man, believed to be in his late 40s, is understood to have dived into the water at the old pier at the southern end of the popular local amenity.
It’s believed the man was seen diving into the water but not resurfacing. It’s also understood that a number of young men who saw him dive in, jumped in after him and managed to reach him and bring him to the surface and then to the lake shore.
The local lifeguard also ran to assist while Gardaí, the National Ambulance Service and Irish Coast Guard were all alerted.
The Shannon-based Irish Coast Guard helicopter, Rescue 115, which had been dealing with another incident in Doonbeg on the Clare coast at the time, was re-tasked from that mission to the unfolding incident in Ennis.
The Doolin unit of the Irish Coast Guard, which had also been tasked to the incident in Doonbeg, were rerouted to the scene in Ennis too.
Efforts to resuscitate the man continued until ambulance paramedics arrived. Despite the best efforts of a number of people to revive the man, he was pronounced dead at the scene.
The Rescue 115 helicopter landed in a field close to the lake in case the casualty needed to be airlifted to hospital, but the helicopter was stood down after it was confirmed the man had passed away.
The man’s body was removed to the mortuary at University Hospital Limerick where a post-mortem examination will be carried out.
Gardaí will also undertake an investigation of the tragedy and prepare a file for the county coroner who will hold an inquest at a later date.
A Garda spokesperson confirmed members attended the scene of the incident.
"A man had dived into the water from the Old Pier. Gardaí and persons at scene assisted the man and he was taken from the water. The man was later pronounced deceased,” they said.
"The man's body was then removed from the scene to Limerick Morgue,” they added.
The incident occurred as the current heat wave continued and many people attended popular water amenities and coastal locations in an effort to enjoy the weather and cool-off from the heat.