Water Safety Ireland is warning that there is an average of five drownings every fortnight in Ireland.
As people flock to lakes and beaches during the warm weather, rescue chiefs are reminding people that while it may be hot, water temperatures are still a good deal cooler.
Water Safety Ireland's Roger Sweeney says cold-water shock is to blame for a lot of tragedy.
"A lot of people are used to swimming in the warmer environment of a swimming pool, indoors, over winter," said Mr Sweeney.
"So for a lot of people, it will be their first time swimming outdoors."
Mr Sweeney advises people to swim at a lifeguarded waterway.
Where that is not possible he said people should "use local knowledge to swim in areas that are known locally as safe."
He said people should swim in places "that have ring buoys that you can use if people get into difficulty."
Separately, investigations are continuing into a swimming tragedy in Louth yesterday.
A 14-year-old girl who got into difficulty while swimming at Seapoint, near Termonfeckin, died last night.