The ESB is reminding people that swimming is not allowed in any of its reservoirs.
In a statement, the electricity supplier said its reservoirs are deep and fast flowing with uneven ground making them extremely dangerous for swimming.
They include the reservoirs at Poulaphoca in Wicklow, Inniscarra and Carrigadrohid in Cork, the Ardnacrusha headrace and tailrace canal in County Clare and Assaroe in County Donegal.
The warning is being made as a result of the current spell of warm weather.